Method for detecting the height of molten material

Abstract

A method for detecting the height of molten material in an ore smelting furnace, having a discharge hole in its lower portion through which the molten material is discharged, includes measuring the discharge distance of the molten material through the discharge hole; calculating the discharge velocity of the molten material through the discharge hole using the discharge distance, the height of the discharge hole, and the discharge angle of the molten material; and detecting the height of the molten material using the discharge velocity.

Description

1 / 20 METHOD FOR DETECTING THE HEIGHT OF MOLTEN MATERIAL TECHNICAL FIELD

[001] The present invention relates to a method for detecting the height of molten material in a smelting furnace. TECHNICAL BACKGROUND

[002] A blast furnace is one of the ore smelting furnaces whose interior cannot be directly observed. The blast furnace is an ore smelting furnace that produces pig iron by charging iron-rich ore and coke through the top of the furnace and blowing a mixture of air, pure oxygen, and the like through a lower portion of the furnace. The molten iron slag produced accumulates in a bottom portion of the blast furnace, and the molten iron slag is discharged out of the furnace through a hole called the tap hole before reaching the blast furnace-related equipment. In the case where such a production method is carried out, it is required to operate the blast furnace stably without difficulties in order to achieve a planned production quantity.

[003] However, molten iron slag is sometimes excessively accumulated in the bottom portion of the blast furnace due to equipment failure to open a tap hole, deterioration of the molten iron slag fluidity, or similar factors. This narrows a gas flow region and therefore deteriorates gas permeability or causes a tuyere to become blocked with molten slag. In the worst-case scenario, production needs to be stopped. Therefore, it is necessary to take advantage of a molten material height for stable operation of an ore melting furnace.

[004] There are techniques for utilizing the height of a molten material in an ore smelting furnace. For example, Patent Literature Petition 870260058978, dated 06 / 17 / 2026, page 11 / 32 2 / 20 discloses obtaining two or more images of a pattern of molten material discharged through a discharge hole of an ore smelting furnace in a short period of time, calculating a discharge velocity of the molten material from a change in the pattern, and then calculating a height of molten material from the discharge velocity and a pressure in the furnace. LIST OF QUOTES PATENTARY LITERATURE

[005] PTL 1: Publication of Unexamined Japanese Patent Application No. 2017-160498 NON-PATENTY LITERATURE

[006] NPL 1: Takashi SUGIYAMA and three others, Analysis of Liquid Flow in the Dripping Zone of a Blast Furnace, Tetsu-to-Hagane, Vol. 73 (1987), No. 15, pp. 2044-2051

[007] NPL 2: Masaki SAWAMOTO, Nagare-No-Rikigaku (hydrodynamics), KYORITSU SHUPPAN CO., LTD., 2005 edition, pp. 58-59 SUMMARY OF THE INVENTION TECHNICAL PROBLEM

[008] However, the molten material flowing through the discharge hole encounters resistance from an inner wall of the discharge hole, and thus the velocity of molten material flowing in contact with the inner wall is lower than the velocity of molten material flowing in the center of the discharge hole. Consequently, the velocity of the external molten material flowing in contact with the inner wall of the discharge hole when discharged through the discharge hole is lower than the velocity of the internal molten material flowing in the center of the discharge hole. Since a pattern in an external portion of molten material discharged through the discharge hole is Petition 870260058978, dated 06 / 17 / 2026, page 12 / 32 3 / 20 photographed, a molten material flow velocity calculated by imaging is lower than an actual discharge velocity. As just described, according to the method disclosed in Patent Literature 1, an accurate discharge velocity of molten material cannot be found and, therefore, the accuracy of calculating a molten material height from the discharge velocity is low. The present invention was made in view of this problem of the conventional technique, and an objective of the present invention is to provide a method for detecting molten material height that can accurately measure a molten material discharge velocity and detect a molten material height with high precision. SOLUTION TO THE PROBLEM

[009] The measures to solve the problem above are as follows. (1) A method for detecting the height of molten material in an ore smelting furnace having, in a lower portion thereof, a discharge hole through which the molten material is discharged, the method for detecting the height of molten material includes: measuring a discharge distance of the molten material discharged through the discharge hole; calculating a discharge velocity of the molten material discharged through the discharge hole using the discharge distance, a discharge hole height and a discharge angle of the molten material; and detecting the height of the molten material using the discharge velocity. (2) The method for detecting molten material height according to (1) additionally includes measuring the height of the discharge hole. (3) The method of detecting molten material height according to (1) or (2), in which the molten material height is detected by using the resistance force that the molten material receives from the discharge hole while it is discharged through the discharge hole and the discharge velocity. Petition 870260058978, dated 06 / 17 / 2026, p. 13 / 32 4 / 20 ADVANTAGEOUS EFFECTS OF THE INVENTION

[010] According to the molten material height detection method according to the present invention, a discharge velocity of the molten material discharged through a discharge hole is calculated by using a molten material discharge distance, a discharge hole height, and a molten material discharge angle. This makes it possible to calculate the molten material discharge velocity more accurately than a method of calculating the molten material discharge velocity by imaging. By detecting a molten material height using the molten material discharge velocity thus calculated, the molten material height can be detected with high accuracy. BRIEF DESCRIPTION OF THE DRAWINGS

[011] [Fig. 1] Fig. 1 is a partial cross-sectional view of a lower portion of a blast furnace 10.

[012] [Fig. 2] Fig. 2 is a schematic view illustrating a situation in which molten material 12 is discharged through a tap hole 14.

[013] [Fig. 3] Fig. 3 is a schematic cross-sectional view of the 14 tap hole through which the molten material 12 passes.

[014] [Fig. 4] Fig. 4 illustrates images of discharge flows from Inventive Example 1 and Inventive Example 2.

[015] [Fig. 5] Fig. 5 is a graph illustrating a result of height H detection of molten material in Inventive Example 1 and Inventive Example 2.

[016] [Fig. 6] Fig. 6 is a graph that illustrates a temporal change in the molten iron slag balance. DESCRIPTION OF THE MODALITIES

[017] The present invention is described below based on a Petition 870260058978, dated 06 / 17 / 2026, p. 14 / 32 5 / 20 embodiment of the invention. In the present embodiment, a blast furnace is used as an ore smelting furnace, and an embodiment of a molten material height detection method is described for detecting a molten material height in the blast furnace. However, the molten material height detection method according to the present invention is applicable not only to a blast furnace, but also to any ore smelting furnace having, in a lower portion thereof, a discharge hole through which the molten material is discharged out of the furnace.

[018] According to the method of detecting molten material height according to the present embodiment, a discharge velocity of the molten material discharged out of the furnace through a discharge hole is calculated, and a height of the molten material accumulated in a lower portion of the blast furnace is detected using the discharge velocity. First, a method for calculating a discharge velocity of the molten material discharged out of the furnace through the discharge hole is described with reference to Figs. 1 to 3.

[019] Fig. 1 is a partial cross-sectional view of a lower portion of a blast furnace 10. The blast furnace 10 has, in a lower portion thereof, several tap holes 14 through which the molten material 12 accumulated in the lower portion is discharged. The molten material 12 is molten iron, molten slag, or a mixture thereof existing as a liquid in the furnace. The molten material 12 is discharged out of the furnace through any of the tap holes 14 to become a parabolic discharge stream 16 and then falls onto a liquid surface 20 of molten material 12 in a slide 18. In the present embodiment, the tap hole 14 is an example of a discharge hole through which the molten material 12 accumulated in the lower portion of the furnace is discharged out of the furnace. Petition 870260058978, dated 06 / 17 / 2026, page 15 / 32 6 / 20

[020] Fig. 2 is a schematic view illustrating a situation in which molten material 12 is discharged through the tap hole 14. According to the molten material height detection method according to the present embodiment, a discharge velocity of the molten material 12 is calculated by using a discharge distance Ltap of the molten material 12, a height htap of the tap hole 14 and a discharge angle θtap of the molten material 12 illustrated in Fig. 2 (a). The discharge distance Ltap of the molten material 12 is a distance from a position where the molten material 12 is discharged through the tap hole 14 to a position where the discharged molten material 12 falls onto a liquid surface of the molten material 12. The discharge distance Ltap can be, for example, measured by using an image obtained by imaging the discharge flow 16 together with a subject used as a length standard.

[021] The height htap of the tap hole 14 is the height from the center of the tap hole 14 to the liquid surface 20 over which the molten material 12 falls. The height from the center of the tap hole 14 to the liquid surface 20 over which the molten material 12 falls can be measured using an image obtained by imaging the discharge flow 16 along with a subject used as a length standard or it can be a projection value of the tap hole 14. Note that the center position of the tap hole 14 changes once a refractory is corroded when the molten material 12 is discharged through the tap hole 14. Furthermore, the height of the liquid surface 20 can also change. It is therefore preferable to measure the height from the center of the tap hole 14 to the liquid surface 20 over which the molten material 12 falls using an image obtained by imaging the discharge flow 16.

[022] The discharge angle θtap of the molten material 12 is an angle formed between the discharge flow 16 formed when the molten material 12 is Petition 870260058978, dated 06 / 17 / 2026, page 16 / 32 7 / 20 discharged through the tap hole 14 and a horizontal plane. The discharge angle θtap can be measured using an image obtained by imaging the discharge flow 16 or it can be identical to a projection value of an angle of inclination of a central axis of the tap hole 14 with respect to a horizontal plane. That is, the height htap of the tap hole 14 and the discharge angle θtap of the molten material 12 do not necessarily need to be measured.

[023] Fig. 2 (b) illustrates how an object 30 that has been launched obliquely moves in a parabolic trajectory. For example, assume that object 30 is launched obliquely from a height h at a launch angle θ and lands after flying for a flight distance L, as illustrated in Fig. 2 (B). Since only gravity acts on object 30, an equation of motion for object 30 is expressed by the following formulas (1) and (2), where x is a left-right direction and z is an up-down direction.

[024] [Formula 1] Im X = 0 · · · (1) dt

[025] [Formula 2] mx — = — mxg · · · (2) dt °

[026] In formula (1) above, vx is an initial velocity (m / s) in the x direction, and in formula (2), vz is an initial velocity (m / s) in the z direction. Furthermore, m is the mass (kg) of object 30, and eg is a gravitational acceleration (9.8 m / s2).

[027] First, a moving distance in the z direction is studied. Assume that a period from the moment object 30 is launched until the moment object 30 lands is Δt seconds, object 30 falls from height h in At seconds. Thus, the following formula (3) is established regarding the moving distance in the z direction. Petition 870260058978, dated 06 / 17 / 2026, page 17 / 32 8 / 20

[028] [Formula 3] —h = —|xgx (At)2+ vinix sin0 x At · · · (3)

[029] In formula (3) above, vini is an initial velocity (m / s) of the object 30, θ is a launch angle (rad) and h is the height (m). In the second term on the right-hand side of formula (3), an initial velocity in the z direction is multiplied by At.

[030] Next, a moving distance in the x direction is studied. Since no force acts in the x direction in the case of oblique launch, an initial velocity in the x direction is maintained until landing. Therefore, assuming that a period from the moment object 30 is launched until the moment object 30 lands is At, object 30 moves the flight distance L in At seconds. Thus, the following formula (4) is established regarding the moving distance in the x direction.

[031] [Formula 4] L = viniX cos0 X At · · · (4)

[032] In formula (4) above, L is a flight distance (M) of object 30 in the x direction. vini is an initial velocity (m / s) of object 30, and θ is a launch angle (rad).

[033] The following formula (5) relating to the initial velocity of object 30 is derived from formulas (3) and (4) above. Note that a height pattern h is a landing position of object 30 in the following formula (5).

[034] [Formula 5]vini=L......-..................... ... (5) y 2xcos26x(Lxtan9+h)

[035] When formula (5) above is applied to the calculation of the discharge velocity Vtap of the molten material 12, Vini is the discharge velocity Vtap (m / s) Petition 870260058978, dated 06 / 17 / 2026, p. 18 / 32 9 / 20 of the molten material 12, L is the discharge distance Ltap (m) of the molten material 12, h is the height htap (m) of the tap hole 14 and θ is the discharge angle θtap (rad) of the molten material 12. Thus, the discharge velocity of the molten material 12 can be calculated by using formula (5) above, the discharge distance Ltap of the molten material 12, the height htap of the tap hole 14 and the discharge angle θtap of the molten material 12. That is, this is a method for estimating the velocity of a molten material by imaging the shape of a discharge flow and combining the photographed shape with an estimation formula based on mechanics, which makes it possible to reduce a velocity measurement error resulting from the resistance of an inner wall of a tap hole and accurately calculate a molten material discharge velocity.

[036] Next, a method for detecting a molten material height 12 from the discharge velocity Vtap is described. According to the molten material height detection method according to the present embodiment, the molten material height 12 is calculated by using the discharge velocity Vtap of the molten material 12 and the following formula (6).

[037] [Formula 6] (- x P1 x vtap2+P1+p1xgxH)-(-xp1x vtap2+P2+p1x gx htap) = 0 · · · (6)

[038] In formula (6) above, pi is a density (kg / m3) of the molten material 12, vtap is the discharge velocity (m / s) of the molten material 12, Pi is a gas pressure (Pa) in the furnace, g is a gravitational acceleration (9.8 m / s2), H is a height (m) of the molten material 12 accumulated in the lowest portion of the furnace, P2 is a gas pressure (Pa) at an outlet of the tap hole 14, and htap is the height (m) of the tap hole 14.

[039] The density pl of the molten material 12 may be a value from a past record. In the case where the molten material 12 includes molten iron slag, the density ρι of the molten material 12 may be calculated by combining Petition 870260058978, dated 06 / 17 / 2026, page 19 / 32 10 / 20 a density of cast iron and a density of molten slag in a mixing ratio of the same. The discharge velocity vtap of the molten material 12 is vinicalculated by formula (5) above. The gas pressure Pi in the furnace is found from a measurement value of a pressure gauge mounted in the lowest portion of the blast furnace 10. The gas pressure P2 at the outlet of the tap hole 14 can be atmospheric pressure. A reference level for the height H of molten material 12 and the height htap of the tap hole 14 in formula (6) above is a bottom position of the blast furnace 10.

[040] The first term on the left-hand side of formula (6) above is a term representing the mechanical energy of the molten material 12 accumulated in the lower portion of the blast furnace 10. The second term on the left-hand side of formula (6) above is a term representing the mechanical energy of the molten material 12 that has just been discharged through the tap hole 14. Note that a kinetic energy term of the molten material 12 accumulated in the lower portion of the furnace is sufficiently smaller than the other terms and, therefore, can be ignored. Formula (6) above is a formula that shows that these types of mechanical energy are equal (a difference between the first term and the second term is 0), and the height H of molten material 12 accumulated in the lower portion of the furnace can be detected by using formula (6).

[041] Fig. 3 is a schematic cross-sectional view of tap hole 14 through which molten material 12 passes. Molten material 12 receives resistance force from tap hole 14 when molten material 12 accumulated in the lower portion of blast furnace 10 is discharged out of the furnace. Therefore, it is preferable to calculate the height H of molten material 12 using the following formula (7), taking into account the influence of resistance force in formula (6) above.

[042] [Formula 7] Petition 870260058978, dated 06 / 17 / 2026, page 20 / 32 11 / 20 1 ( 2xPlX Vtap2+P1 + Pi xgxH)-(-xp1x Vtap2+ P2+P1xgx htap) W 1 = ( 7X ftapX* PlX V^P2)+( 2X Κβ XPlXW )

[043] In formula (7) above, ftap is a barrel friction coefficient (-) of the 14-hole, Wtap is a length (m) of the 14-hole, Dtap is an internal diameter (m) of the 14-hole and Ke is an inlet loss coefficient for the barrel (-). Note that (-) means dimensionless.

[044] The Wtap length of the 14-hole run hole is found from the intrusion length of a drill bit for forming the run hole. 14. The internal diameter Dtap of the race hole 14 is found from a diameter of a drill bit used to form the race hole 14. The pipe friction coefficient ftap of the race hole 14 can be calculated by the Swamee-Jain equation indicated by the following formula (8).

[045] [Formula 8] fxtap 0.0626 [iog(- +gâo]2tapJ• · (8)

[046] In formula (8) above, etap is the surface roughness of the race hole (m), Dtap is the internal diameter (m) of the race hole 14 and Re is a Reynolds number (-) of a fluid flowing through the race hole 14.

[047] Although the surface roughness of a run hole varies depending on a hole opening method, a run hole mixture, a period elapsed since the start of flow or the like, it has been confirmed by operational analysis that it is appropriate to use a value within a range of 0.0001 m 0.01 m. The Reynolds number Re can be calculated by the following formula (9).

[048] [Formula 9] Petition 870260058978, dated 06 / 17 / 2026, page 21 / 32 12 / 20 Re = ... (ç)

[049] In formula (9) above, μ is the viscosity (Pa^s) of the molten material 12. The viscosity μ of the molten material 12 is calculated by combining the viscosity of the molten iron and the viscosity of the slag in a mixing ratio of the same. The viscosity of the molten iron and the viscosity of the molten slag may be values ​​from previous records or the viscosity of the molten slag may be estimated by a method described in the Non-Patent Literature 1 for estimating viscosity from concentrations of components such as CaO, MgO, AbO3, SiO2 and FeO and a temperature.

[050] The inlet loss coefficient for the pipe Ke can be calculated using the following formula (10) described in Non-Patent Literature 2.

[051] [Formula 10] Ke = 0.5 + 0.3 x sin(0tap) + 0.2 x sin2(0tap) · · · (10)

[052] In formula (10) above, θtap is the discharge angle (rad) of the molten material 12.

[053] As described above, according to the molten material height detection method according to the present embodiment, the discharge velocity vtap of the molten material 12 discharged out of the furnace through the tap hole 14 is calculated by using the discharge distance Ltap of the molten material 12 discharged through the tap hole, the height htap of the tap hole 14 and the discharge angle θtap of the molten material 12. This makes it possible to calculate the discharge velocity vtap of the molten material 12 more accurately than the method for finding the discharge velocity of the molten material 12 by imaging a pattern in the molten material 12.

[054] So, the height H of molten material 12 is calculated using the Petition 870260058978, dated 06 / 17 / 2026, p. 22 / 32 13 / 20 calculated discharge velocity vtap of molten material 12 and, formula (6) above shows that the mechanical energy of the molten material 12 accumulated in the lowest portion of the furnace and the mechanical energy of the molten material 12 that has just been discharged out of the furnace through the tap hole 14 are equal. According to the molten material height detection method according to the present embodiment, the height H of molten material 12 is calculated by using the discharge velocity vtap of molten material 12 which is calculated more accurately than the method for finding the discharge velocity of molten material 12 by imaging a pattern in molten material 12 and, in this way, the accuracy of detecting the height H of molten material 12 also improves.

[055] Furthermore, it is preferable to use formula (7) above taking into account the resistance force that the molten material 12 receives from the run hole 14 instead of formula (6) above in the case where the height H of molten material 12 is detected. This can achieve a further improvement in the accuracy of detecting the height H of molten material 12. EXAMPLE

[056] The following is an Example in which the suitability of the molten material height detection method according to the present embodiment was examined using a large blast furnace having a capacity of approximately 5,000 m3. In the present Example, a molten material discharge flow immediately after hole opening was photographed, and a discharge distance Ltap and a height htap of a tap hole were measured from an image generated by imaging. The discharge flow was photographed using a video camera whose guaranteed operating temperature is 70 °C and which can acquire image data of an image size of 2064 χ 1544. In the present Example, the discharge flow was Petition 870260058978, dated 06 / 17 / 2026, page 23 / 32 14 / 20 photographed twice at different times using the video camera. An example in which the discharge velocity vtap and the height H of molten material were detected from an image obtained by the first imaging is referred to as Inventive Example 1, and an example in which the discharge velocity vtap and the height H of molten material were detected from an image obtained by the second imaging is referred to as Inventive Example 2.

[057] Fig. 4 illustrates images of discharge streams from Inventive Example 1 and Inventive Example 2. Fig. 4 (a) illustrates an image of a discharge stream from Inventive Example 1, and Fig. 4 (b) illustrates an image of a discharge stream from Inventive Example 2. As illustrated in Figs. 4 (a) and 4 (b), a surface portion of each of the discharge streams, namely a boundary plane between the discharge stream and the ambient air, is not a smooth surface but an irregular wave-like shape. This indicates that the surface portion of the discharge stream receives strong viscosity resistance from an inner wall of a discharge hole and from the ambient air, and thus the discharge stream is disturbed only in the vicinity of a surface layer of the discharge stream.It has been confirmed that the calculation method according to the present invention is superior in accuracy, for example, to a conventional method of estimating a flow rate from a change in position in an image, since the flow rate of the discharge flow in the vicinity of the surface layer fluctuates irregularly due to the disturbed flow. In Inventive Example 1 and Inventive Example 2, the discharge distance Ltap and the height htap of the runner hole were measured from the images, and the discharge velocity vtap was calculated using the discharge distance Ltap and the height htap of the runner hole. Table 1 below shows the measurement results of the discharge distance Ltap and the height htap of the runner hole, the inclination angle θtap of the runner hole, and the discharge velocity. Petition 870260058978, dated 06 / 17 / 2026, p. 24 / 32 15 / 20 vtap·

[058] [Table 1] Inventive Example 1 Inventive Example 2 Discharge distance (Ltap) (m) 2.5 2.2 Hose height (htap) (m) 0.6 0.3 Hose inclination angle (tap) (°) 7 7 Discharge velocity (vtap) (m / s) 5.86 6.50

[059] Furthermore, the molten material heights H in Inventive Example 1 and Inventive Example 2 were calculated using the discharge velocity vtap. Table 2 below shows the parameters used to calculate the molten material heights H.

[060] [Table 2] Inventive Example 1 Inventive Example 2 Flow velocity (m / s) 5.86 6.50 Pressure in the furnace (lowest portion of the furnace) (Pa) 4.56x10⁵ Atmospheric pressure (Pa) 1.01x10⁵ Tap hole diameter (m) 0.065 Tap hole surface roughness (m) 0.001 Tap hole length (m) 3.8 3.7 Density of cast iron (kg / m³) 6700 Density of molten slag (kg / m³) 2650 Viscosity of cast iron (Pa⁻¹s²) 0.006 Viscosity of molten slag (Pa⁻¹s²) 0.435 Petition 870260058978, dated 06 / 17 / 2026, page 25 / 32 16 / 20 Inventive Example 1 Inventive Example 2 n ~ . r _ (cast iron / Volume ratio of cast iron , , , , ... cast iron + slag) 0.41 0.42

[061] Fig. 5 is a graph illustrating a result of the detection of the molten material heights H in Inventive Example 1 and Inventive Example 2. Both the molten material height H detected in Inventive Example 1 and the molten material height H detected in Inventive Example 2 were between the tap hole height and the tuyere height. The molten material height H detected in Inventive Example 2, in which the discharge velocity was greater than in Inventive Example 1, was greater than in Inventive Example 1.

[062] Next, the adequacy of the calculated result of the molten material height H illustrated in Fig. 5 was examined using the molten iron slag balance, which are blast furnace operating data. The molten iron slag balance is a value obtained by subtracting the amount of molten iron slag generated from the amount of molten iron slag flowed out in terms of volume. A molten iron slag balance of 0 means that the amount of molten iron slag flowed out and the amount of molten iron slag generated are equal. A molten iron slag balance greater than 0 means that the amount of molten iron slag flowed out is greater than the amount of molten iron slag generated, and thus the amount of molten material accumulated in a lower portion of a furnace decreases, and the molten material height H decreases accordingly.On the other hand, a molten iron slag balance of less than 0 means that the amount of molten iron slag drained is less than the amount of molten iron slag generated, and thus, a quantity of molten material accumulates in a lower portion of a furnace. Petition 870260058978, dated 06 / 17 / 2026, p. 26 / 32 17 / 20 increases, and therefore the height H of molten material increases.

[063] The amount of molten iron slag generated was calculated from an amount of blast furnace oxygen per unit time, a proportion of oxygen contained in the iron oxide in the raw materials charged through the furnace top and a proportion of gangue in the charged raw materials. Specifically, an amount of molten iron generated was calculated using the following formula (11), and an amount of molten slag generated was calculated using the following formula (12), and an amount of molten iron slag generated was calculated by summing these amounts. Wp = (Ntop - Ntuy) X (RFe / o) X MFe - RFeHM ... (11) Ws = Wp X RG / Fe ... (12)

[064] In formulas (11) and (12) above, Wp is the amount of molten iron generated (t / time), and Ws is the amount of molten slag generated (t / time). Ntop is a quantity of substance (mol / time) of oxygen atoms in the furnace top gas per time, Ntuy is a quantity of substance (mol / time) of oxygen atoms blown through a tuyere per time, RFe / O is an average number (-) of iron atoms per oxygen atom in iron oxide in the raw materials charged through the furnace top, MFe is the molar mass (t / mol) of iron, RFeHM is a mass fraction (-) of iron in molten iron, and RG / Fe is the mass (t / molten iron) of gangue charged per 1 t of molten iron.

[065] Ntop is found by component analysis of furnace top gas. Ntuy is found by component analysis of gas blown through the tuyere. RFe / O and RG / Fe are found by component analysis of raw materials charged through the furnace top. RFeHM is found by component analysis of molten iron flowing through a tap hole.

[066] Fig. 6 is a graph that illustrates a temporal change of Petition 870260058978, dated 06 / 17 / 2026, page 27 / 32 18 / 20 cast iron slag balance. The moment of Inventive Example 1 illustrated in Fig. 6 is a moment in which the discharge flow imaging was performed as Inventive Example 1. The moment of Inventive Example 2 is a moment in which the discharge flow imaging was performed as Inventive Example 2.

[067] As is clear from the temporal change in the molten iron slag balance, the amount of molten material accumulated in the lower portion of the furnace increases from the time of Inventive Example 1 to the time of Inventive Example 2. Consequently, the height H of molten material accumulated in the lower portion of the blast furnace is higher at the time of Inventive Example 2 than at the time of Inventive Example 1. The height H of molten material detected by the molten material height detection method according to the present embodiment is also greater in Inventive Example 2 than in Inventive Example 1, as illustrated in Fig. 5, and thus the same trend is observed.

[068] Next, the result of detecting the height H of molten material illustrated in Fig. 5 was examined using the molten material height balance, and a result of the examination is described below. The molten material height balance is calculated from the molten iron balance and the molten slag balance. The molten iron balance is a value obtained by subtracting a quantity of molten iron (t) generated from a quantity of molten iron (t) flowed in the target flow, and the molten slag balance is a value obtained by subtracting a quantity of molten slag (t) generated from a quantity of molten slag (t) flowed. In the case where the values ​​of these balances are negative, the quantity of molten iron slag in the furnace increases, and in the case where the values ​​of these balances are positive, the quantity of molten iron slag in the furnace decreases. Since these Petition 870260058978, dated 06 / 17 / 2026, page 28 / 32 19 / 20 balances are expressed in weights (t), these balances can be converted into molten material height balance by dividing these balance values ​​by a density and a sill cross-sectional area. Specifically, the molten material height balance was calculated using the cast iron balance, the molten slag balance and the following formula (13). Cast material height balance = [cast iron balance (t) / cast iron density (kg / m3) + cast slag balance (t) / cast slag density (kg / m3)] / effective cross-sectional area of ​​hearth (m2) ... (13)

[069] Table 3 below shows the cast iron balance, molten slag balance, and molten material height calculated using these balances at the time of Inventive Example 1 and at the time of Inventive Example 2 illustrated in Fig. 6. Note that the effective hearth cross-sectional area (m2) in formula (13) above was calculated by multiplying the cross-sectional area of ​​the lowest part of the furnace by a void fraction of the lowest portion of the furnace, which was adjusted to 0.35 based on previous records.

[070] [Table 3] Inventive Example 1 Inventive Example 2 Cast iron balance (t) -285 -693 Molten slag balance (t) 351 707 Molten material height balance (m) -0.89 -2.52

[071] As illustrated in Table 3, a difference in the height of the molten material between the moment of Inventive Example 1 and the moment of Inventive Example 2 calculated from the molten material height balance was 1.63 m (-0.89 - (-2.52) = 1.63). It was thus revealed that a difference between the height of the molten material of Inventive Example 1 and the height of the molten material of Inventive Example 2 illustrated in Fig. 5 is almost the same as this Petition 870260058978, dated 06 / 17 / 2026, pp. 29 / 32 20 / 20 difference of 1.63 m in molten material height calculated from the molten material height balance. This result confirmed that molten material height in a blast furnace can be detected with high accuracy when using the molten material height detection method according to the present embodiment. LIST OF REFERENCE SIGNS blast furnace molten material tap hole discharge flow slide liquid surface object Petition 870260058978, dated 06 / 17 / 2026, pp. 30 / 32

Claims

1 / 2 CLAIMS 1. A method for detecting the height of molten material, for detecting the height of molten material in an ore melting furnace (10) having, in a lower portion thereof, a discharge hole (14) through which the molten material (12) is discharged, the method for detecting the height of molten material characterized in that it comprises: measuring a discharge distance of the molten material (12) discharged through the discharge hole (14); calculating a discharge velocity of the molten material (12) discharged through the discharge hole (14) by using the discharge distance, a height of the discharge hole (14) and a discharge angle of the molten material (12), and formula (5); and detecting the height of molten material by using the discharge velocity, the gas pressure in the furnace, the gas pressure at the outlet of the discharge hole, and formula (6); formula (5): gxL2 ...β) 2xcos20x(Lxtan0+h) where Vini represents the discharge velocity Vtap (m / s) of the molten material, L represents the discharge distance (m) of the molten material, h represents the height htap (m) of the tap hole and θ represents the discharge angle θtap (rad) of the molten material formula (6): 1 1 ( - x P1 x vtap2 +P1+p1xgxH)-(-xp1x Vtap2+P2+P1 xgx htap ) = 0 · · · (6) where ρι represents a density (kg / m3) of the molten material, vtap represents the discharge velocity (m / s) of the molten material, Pi represents Petition 870260058978, of 17 / 06 / 2026, page. 31 / 32 2 / 2 a gas pressure in the furnace (Pa), g represents a gravitational acceleration (9.8 m / s2), H represents a height (m) of the molten material accumulated in the lowest portion of the furnace, P2 represents a gas pressure (Pa) at an outlet of the tap hole, and htap represents the height (m) of the tap hole.

2. Method for detecting the height of molten material, according to claim 1, characterized in that it further comprises measuring the height of the discharge hole (14).

3. Method for detecting the height of molten material, according to claim 1 or 2, characterized in that: the height of molten material is detected by using the resistance force that the molten material (12) receives from the discharge hole (14) while being discharged through the discharge hole (14) and the discharge velocity. Petition 870260058978, dated 17 / 06 / 2026, p. 32 / 32

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