KR100376524B1 - Method for predicting shape of dead man in shaft type reduction furnace - Google Patents

Abstract

PURPOSE: A method for predicting shape of dead man in shaft type reduction furnace is provided to increase analysis accuracy of furnace circumstances inside the shaft type reduction furnace by accurately predicting shape of the dead man using dropping and discharging behavior of charging materials in the shaft type reduction furnace. CONSTITUTION: In a method for predicting shape of dead man formed in the lower central part of shaft type reduction furnace having a screw type discharging unit, the method for predicting shape of the dead man in the shaft type reduction furnace comprises the steps of measuring dropping distance and dropping time of dropping object dropped through simulation test, calculating dropping speeds of the dropping object from the measured dropping distance and dropping time of the dropping object, and actually measuring height of the dead man formed after the dropping object is dropped per the calculated dropping speeds; obtaining a correlational expression thereof by plotting the calculated dropping speeds of the dropping object and the actually measured height of the dead man; measuring dropping distance and dropping time of charging materials charged into actual reduction furnace from the upper side, calculating dropping speed of charging material layer from the measured dropping distance and dropping time of the charging materials, and obtaining height of the dead man of the actual reduction furnace by substituting the calculated values for the correlational expression; determining a tip position point of screw of the reduction furnace as coordinate points at both ends of the lower part of the dead man; and representing shape of the dead man in a quadratic expression using the obtained height of the dead man and coordinate points, and determining trajectory of the obtained quadratic expression as the shape of the dead man formed at a dropping time point.

Description

Method of Estimating Core Shape in Shaft Type Reduction Furnace

The present invention relates to a method for estimating the size and shape of a furnace bottom stagnation zone formed in a shaft type reducing furnace having a screw-type discharge unit.

The furnace is a reaction furnace in which there exists a softened melt-bonding zone which governs reaction and air permeability in the furnace, and a melt is present in the lower part and only a solid packing layer is present in the upper part.

On the other hand, the shaft-type reduction furnace is a reactor used mainly for producing directly reduced iron, in which only the shaft portion of the furnace exists, and only the solid-gas reaction and heat exchange occur. The role of the shaft-type reduction furnace is to produce an appropriate level of direct reduced iron by reducing ore to gas. In the reduction furnace, the gas flow is very important for the ore reduction reaction and the uniform gas flow distribution depends on the effective charge distribution. Since the effective charge distribution depends on stable charge drop and discharge, the role of the core in the furnace, which has a great influence on the discharge of the charge, is very important.

In the blast furnace, due to the characteristics of the equipment, a stagnation layer called the core is formed on the soft melt layer and the lower melt layer, indicating the sub-bottom activation state. Therefore, the core shape estimation has been recognized as a very important factor in the furnace operation together with soft welding. However, in the blast furnace, it is difficult to estimate the melt as a liquid coexisting with the core, and confirmation by simulation is mainly performed in a solid-gas state in the cold, so that there is a problem that there are many differences from the situation under the furnace.

On the other hand, in the shaft-type reduction furnace, only the movement of solids in which no liquid exists is considered, so the behavior of the charged material is not complicated as compared with the blast furnace, and only gas and solid reaction occurs in the furnace reaction surface. Only the behavior of the stay can be grasped. As a method for judging the gas flow in a shaft type reduction furnace, there is a calculation method proposed by Tetsu-to-Hagane, vol. 71, 1985, page 47. However, Since the core shape, which is the stagnation layer at the lower center, is assumed to have an arbitrary inclination angle and height, the computation process is complicated and the core shape can not be accurately estimated, so that the calculation result also fails to accurately simulate the actual in- . In addition, since the behavior of the high stagnation under the furnace is also dominated by the shape of the core, accurate estimation of the shape of the core in the shaft type reduction furnace is also essential for the analysis of the high stagnation rate. In the conventional shaft type reduction furnace analysis, .

SUMMARY OF THE INVENTION The present invention has been made to solve the above-mentioned problems, and it is an object of the present invention to improve the degree of analysis of the sulfur content in the shaft-type reduction furnace by accurately estimating the shape of the core using the charge drop and discharge behavior in the shaft type reduction furnace.

1 is a schematic view explaining a loading drop behavior in a shaft type reduction furnace;

Fig. 2 is a schematic view for explaining the discharge behavior at the time of discharge of the charge in the shaft-

Fig. 3 is a graph showing the relationship between the rate of drop of the charge in the shaft type reduction furnace and the height of the core

4 is a graph showing an example of a shape of a core in a sharp reduction reactor

Fig. 5 is a graph showing the core shape estimated by the present invention

According to another aspect of the present invention, there is provided a method for estimating the shape of a core formed in a center portion of a furnace of a shaft type reduction furnace having a screw-

Measuring the distance and time of falling objects falling through the simulation, calculating the falling speed of the falling object, and measuring the height of the core formed after the falling object falls according to the calculated falling speed;

Calculating a falling velocity of the falling object and a measured height of the core according to the above-described equation to obtain a correlation equation;

Calculating the dropping distance and dropping time of the charge charged from the upper portion of the actual reduction path, calculating the dropping speed of the charge layer from the dropping distance, and assigning the calculated value to the correlation formula to obtain the height of the core of the actual reduction furnace ;

Determining a tip position point of the screw of the reducing furnace as a coordinate point of both ends of the lower core; And

Determining the shape of the core by a quadratic equation using the height of the actual core obtained above and the coordinate point and defining the trajectory of the obtained quadratic equation as the shape of the core formed at the time of the descent; The present invention relates to a method of estimating a core shape of a shaft-type reduction furnace.

Hereinafter, the present invention will be described in detail with reference to the drawings.

FIG. 1 is a diagram illustrating the descent and discharge patterns of a falling object using a tracer in the reduced model used in the present invention. FIG.

In the simulated reduction furnace, a screw (1) for discharging fall objects by rotational movement is provided as a discharge device without forward and backward movement, and the surface shape (2) of falling objects falling from the charging device is shaped like an M- And the discharge mode changes to the W-shaped (5) under the influence of the screw at the lower portion of the gas intake port (4).

Due to the nature of the screw discharge device, the drop is preferentially discharged from the lower part of the reduction furnace toward the tip of the screw 1a, and the dropping rate is relatively slow at the center of the reducing furnace and the lower part of the reduction furnace, It can be seen that a stagnation occurs that is slow or does not replace at all.

Fig. 2 is a more detailed simulation of the discharge behavior in the reduction furnace, which is a reduction model. The discharge shape at the start of discharge of the falling object through the full rotation of the screw at the beginning of the operation was W-shaped (6) and changed to W-shaped (7) in which the stagnation layer of the furnace wall was considerably reduced after elapse of a long time after the discharge started. It can be seen that the shape of the core part of the stagnation layer in the center of the furnace has a parabolic shape once the discharge progresses, and the change of the shape and size of the core is small even though the surface part of the core is partially replaced even after a long time.

Therefore, in the present invention, the shape of the core is defined as the discharge pattern at the time when the charge starts to be discharged, and the shape of the core can be estimated as a parabolic shape.

However, in the field of operation, the charge descent and discharge rates change as a result of various operating conditions, thus changing the size and shape of the core in the furnace. However, the loading docking behavior in the reductiion furnace can be measured by the simple calculation by measuring the dropping distance and dropping time of the falling material, but the core size is difficult to measure.

However, it can be considered that the height of the core in the reduction furnace has a certain correlation because the lowering rate of the charge becomes smaller. Based on these conclusions, the change of the fall height of the core, which depends on the shape of the core, is shown in Fig. As shown in FIG. 3, it was confirmed that the relationship between the falling velocity of the falling object and the core height has the following relationship.

H = aV + b

Here, H: core height (cm)

V: descending speed (cm / min)

a, b: constant obtained from experiment

Therefore, the falling distance and the fall time of the charge charged from the upper portion of the actual reducing furnace are measured, the descending speed of the charge water layer is calculated from the falling distance, and the calculated value is substituted into the correlation formula, Can be obtained.

On the other hand, as shown in FIG. 2, the core shape 8 has an exit angle based on the intrinsic angle of repose of the charge itself after the recharging empty work is completed, that is, most of the charge is completely discharged through the screw, Both the lower ends of the core and the end of the screw coincide with each other, so that it is confirmed that both ends of the lower end of the core are almost fixed regardless of the shape of the core.

That is, in the present invention, by utilizing the core characteristics identified above, the position point 1a of both screw ends determined by equipment specifications and the vertex (height) of the parabolic core shape are used as basic data, It is possible to estimate the parabolic-shaped core size and shape.

Fig. 4 shows coordinate points of two points of the core of the core and the tip of the screw in the shaft-type reduction furnace obtained in Fig. 3, which determine the core shape. At this time, the core shape is represented by substituting the three coordinate points in Fig. 4 into the general expression of the parabolic curve expressed by the following quadratic expression.

Y = cX ² + dX + e

Where Y is the distance from the charging baseline to the surface of the core (cm)

X: Distance from furnace center (cm)

c, d, e: constant

3, the shape of the core can be represented by the trajectory of the quadratic equation, and this trajectory can be expressed at a certain point, that is, at a certain point in time And the shape of the core formed at the time point.

Hereinafter, the present invention will be described in detail with reference to examples.

Example

Using a 1/15 scale reduction model of a shaft type reduction furnace having an internal volume of 2260 m 3, a core shape according to the charge drop and discharge behavior in the shaft type reduction furnace was estimated under the experimental conditions shown in Table 1 below, Respectively.

Fig. 5 shows the shape of the core estimated by the method of the present invention, in which the shape of the core varies depending on the change in the charge drop rate based on the result of the core height obtained from the charge drop rate in Fig. 3, It was confirmed that it appeared as parabolic shape.

As described above, according to the method of the present invention, it is possible to accurately determine the size and shape of the core as the stagnation layer from the results of measurement of the charge drop rate in the shaft-type reduction furnace, It provides boundary conditions and makes stable load reduction and discharge possible for furnace under load, which makes it possible to operate stable shaft type reduction furnace.

Claims (3)

A method for estimating the shape of a core formed in a furnace bottom center portion of a shaft type reduction furnace having a screw type discharge device, Measuring the distance and time of falling objects falling through the simulation, calculating the falling speed of the falling object, and measuring the height of the core formed after the falling object falls according to the calculated falling speed; Calculating a falling velocity of the falling object and a measured height of the core according to the above-described equation to obtain a correlation equation; Calculating the dropping distance and dropping time of the charge charged from the upper portion of the actual reduction path, calculating the dropping speed of the charge layer from the dropping distance, and assigning the calculated value to the correlation formula to obtain the height of the core of the actual reduction furnace ; Determining a tip position point of the screw of the reducing furnace as a coordinate point of both ends of the lower core; And Determining the shape of the core by a quadratic equation using the height of the actual core obtained above and the coordinate point and defining the trajectory of the obtained quadratic equation as the shape of the core formed at the time of the descent; Wherein the shape of the core-type reduction furnace of the shaft-type reduction furnace is determined based on the shape of the core-type reduction furnace. 2. The method of claim 1, H = aV + b Where H: core height (cln) V: descending speed (cm / min) a, b: constant obtained from experiment . ≪ / RTI > 2. The method of claim 1, wherein the locus for the core shape Y = cX ² + dX + e Where Y is the distance from the charging baseline to the surface of the core (cm) X: Distance from furnace center (cm) c, d, e: constant . ≪ / RTI >