Methods and devices for detecting the liquid and molten material level and operating methods for vertical furnaces

Abstract

This invention provides a method for detecting the liquid level of a molten material with high accuracy based on the residual amount of the molten material, and an operating method for a vertical furnace using this method. The method involves blowing oxygen-containing gas into the bottom of the vertical furnace, generating high-temperature reducing gas by burning carbon, melting and reducing iron source material (which is loaded from the top of the furnace and forms a solid filling structure within the furnace) using the high-temperature reducing gas to produce a molten material, and then discharging the molten material through the tap hole. The method measures the liquid level of the molten material remaining at the bottom of the furnace after discharge. Specifically, the porosity of the solid filling structure is calculated, and the calculated porosity and the residual amount of molten material after discharge are used to detect the liquid level of the molten material after discharge.

Description

Technical Field

[0001] This invention relates to a method and apparatus for detecting the liquid level height of a liquid, a method and apparatus for detecting the liquid level height of molten material in a vertical furnace, and an operating method for the vertical furnace. Background Technology

[0002] For example, in a vertical furnace such as a blast furnace, iron ore and coke, which serve as raw materials, are charged into the furnace from the top, and hot air is blown in through tuyeres located at the bottom of the furnace. The coke is burned by the hot air blown in through the tuyeres, generating high-temperature reducing gases. The iron ore is melted and reduced by these high-temperature reducing gases to produce molten iron. The molten iron and the slag produced during the iron-making process (hereafter sometimes referred to as "slag") accumulate at the bottom of the furnace and are discharged from the taphole at a constant cycle.

[0003] In blast furnace operation, controlling the residual amount of molten iron and slag at the bottom of the furnace, as well as the height of the molten material level, is crucial for determining the tapping cycle and ensuring stable and economical operation. If the residual amount of molten material increases and the molten material level becomes too high, fluctuations in the blast pressure can become significant, making it impossible to maintain stable operation. Furthermore, if the molten material level rises to near the tuyeres, tuyeres can become blocked due to slag, potentially rendering the furnace inoperable in the worst-case scenario. Stabilizing the blast furnace due to an unstable molten material level requires measures such as increasing the amount of coke charged from the top or changing the amount of hot air blown into the furnace from the tuyeres, which increases the operating costs of the blast furnace.

[0004] As a technique for obtaining the residual amount of molten material, Patent Document 1 discloses the following method: an electrode is installed on the side of the blast furnace, and the voltage is measured by flowing current through the electrode; the liquid level of the molten material is then measured based on the measured voltage. Patent Document 2 discloses the following method: the flow of molten iron and slag discharged from the tap hole is photographed with a camera, the discharge speed of the molten iron and slag is calculated based on the image, and the residual amount of molten material in the blast furnace is estimated based on the discharge speed.

[0005] Existing technical documents

[0006] Patent documents

[0007] Patent Document 1: Japanese Patent Application Publication No. 2006-176805

[0008] Patent Document 2: Japanese Patent Application Publication No. 2017-160498

[0009] Non-patent literature

[0010] Non-patent literature 1: Sugiyama Takashi, and 3 others, “Analysis of liquid flow in the blast furnace drip zone”, Iron and Steel, No. 73 (1987), No. 15, pp. 2044-2051 (Sugiyama Takashi and 3 others, “Analysis of liquid flow in the blast furnace drip zone”, Iron and Steel)

[0011] Non-patent document 2: "Iron and Steel Property Values ​​Compendium" Ironmaking Edition (2006), Japan Iron and Steel Association, p. 437 ("Iron and Steel Property Values ​​Compendium" Ironmaking Edition (2006), Japan Iron and Steel Association)

[0012] Non-Patent Literature 3: Yusuke Kashiwabara, 4 others, “The Influence of Undisappeared Mixed Small Pieces of Coke on the Ventilation of the Lower Part of the Blast Furnace”, Iron and Steel, Vol. 102 (2016), No. 12, pp. 661-668 (Yusuke Kashiwabara, 4 others, “The Influence of Undisappeared Mixed Small Pieces of Coke on the Ventilation of the Lower Part of the Blast Furnace”, Iron and Steel)

[0013] Non-patent document 4: Nouchi Yasuhei, two others, "The influence of the operation and tapping methods on the drainage properties of the blast furnace hearth", Iron and Steel, Vol. 92 (2006), No. 12, P269-274 (Nouchi Yasuhei, two others, "The influence of the operation and tapping methods on the slag drainage properties of the blast furnace hearth") Summary of the Invention

[0014] The problem that the invention aims to solve

[0015] However, the methods disclosed in Patent Documents 1 and 2 require the installation of special sensors and cameras in environments that generate dust, etc., to measure the resistance, potential, or velocity of the tapped slag flow caused by the molten material in the blast furnace. Therefore, implementing these methods incurs not only initial costs for the introduction of special sensors and cameras, but also maintenance costs for these devices. On the other hand, by detecting the residual amount of molten material using the material balance between the amount of molten slag produced and the amount discharged from the tap hole, and dividing this residual amount by the porosity at the bottom of the furnace, the liquid level of the molten material can be detected without the use of special sensors or cameras. However, since the state of the coke filled at the bottom of the furnace varies, the porosity at the bottom of the furnace is considered constant when detecting the liquid level of the molten material, resulting in problems such as the inability to detect the liquid level of the molten material with high accuracy. The present invention addresses these problems of the prior art, and its object is to provide a method and apparatus for detecting the liquid level of the molten material with high accuracy based on the residual amount of molten material, as well as an operating method for a vertical furnace using this detection method. In addition, another object of the present invention is to provide a method and apparatus for detecting the liquid level of a liquid in a container that has been formed by filling it with solids, and which is not limited to a vertical furnace, but can detect the liquid level of a liquid with high accuracy.

[0016] Methods for solving problems

[0017] The methods used to solve the above problems are as follows.

[0018] [1] A method for detecting the liquid level of a liquid is a method for detecting the liquid level of a liquid remaining at the bottom of a container after the liquid contained in the container, which has been filled with a solid filling structure by filling it with a solid and is immersed in at least a portion of the voids of the solid filling structure, is discharged from a discharge hole provided at the bottom of the container. The method involves calculating the porosity of the solid filling structure and using the calculated porosity and the amount of liquid remaining after the discharge to detect the liquid level after the discharge.

[0019] [2] According to the liquid level detection method of [1], the porosity of the solid filling structure is calculated using the tilt angle of the liquid level at the end of the discharge of the liquid from the discharge hole.

[0020] [3] A method for detecting the liquid level height of a molten material is a method for detecting the liquid level height of a molten material remaining at the bottom of a vertical furnace after the molten material has been discharged from the furnace. The method involves blowing oxygen-containing gas into the bottom of a vertical furnace, generating high-temperature reducing gas by burning carbon, melting and reducing iron source raw materials loaded from the top of the vertical furnace and forming a solid filling structure in the vertical furnace using the high-temperature reducing gas to produce a molten material, and discharging the molten material from the tap hole of the vertical furnace. The method involves calculating the porosity of the solid filling structure and using the calculated porosity and the amount of molten material remaining after discharge to detect the liquid level height of the molten material after discharge.

[0021] [4] According to the method for detecting the liquid level of the molten material described in [3], the porosity of the solid filling structure is calculated using the inclination angle of the liquid level of the molten material at the end of the discharge of the molten material from the iron outlet.

[0022] [5] According to the method for detecting the liquid level height of the melt as described in [3] or [4], the porosity is calculated using the viscosity of the melt calculated based on the component concentration of the discharged melt and the temperature of the melt.

[0023] [6] The method for detecting the liquid level height of the melt according to any one of [3] to [5] uses the discharge rate at the end of the discharge of the melt, calculated based on the discharge amount, discharge time and initial discharge rate of the melt, to calculate the porosity.

[0024] [7] An operating method for a vertical furnace, wherein if the liquid level detected by the liquid level detection method of any one of [3] to [6] exceeds a predetermined threshold, at least one of the following operations is performed: reducing the manufacturing speed of the melt and discharging the melt.

[0025] [8] A liquid level detection device is used to detect the liquid level of liquid remaining at the bottom of a container after the liquid contained in the container, which has been filled with a solid filling structure to form a solid filling structure and is immersed in at least a portion of the voids of the solid filling structure, is discharged from a discharge hole provided at the bottom of the container. The device includes a liquid level detection unit that calculates the porosity of the solid filling structure and uses the calculated porosity and the amount of liquid remaining after the discharge to detect the liquid level after the discharge.

[0026] [9] According to the liquid level detection device of [8], the liquid level detection unit calculates the porosity of the solid filling structure using the tilt angle of the liquid level at the end of the discharge of the liquid from the discharge hole.

[0027]

[10] A device for detecting the liquid level of a molten material is used in a vertical furnace in which oxygen-containing gas is blown into the lower part of the furnace, high-temperature reducing gas is generated by burning carbon, iron source material loaded from the top of the furnace and forming a solid filling structure in the furnace is melted and reduced by the high-temperature reducing gas to produce a molten material, and the molten material is discharged from the tap hole of the furnace. The device detects the liquid level of the molten material remaining at the bottom of the furnace after the molten material is discharged. The device includes a liquid level detection unit that calculates the porosity of the solid filling structure and uses the calculated porosity and the amount of molten material remaining after the discharge to detect the liquid level of the molten material after the discharge.

[0028]

[11] According to the molten liquid level detection device described in

[10] , the liquid level detection unit calculates the porosity of the solid filling structure using the inclination angle of the molten liquid level at the end of the discharge of the molten liquid from the tap hole.

[0029]

[12] According to the liquid level detection device of

[10] or

[11] , the liquid level detection unit uses the viscosity of the melt calculated based on the component concentration of the discharged melt and the temperature of the melt to calculate the porosity.

[0030]

[13] The liquid level detection device for the melt according to any one of

[10] to

[12] , wherein the liquid level detection unit calculates the porosity using the discharge rate at the end of the discharge of the melt, which is calculated based on the discharge amount, discharge time and initial discharge rate of the melt.

[0031] Invention Effects

[0032] In the detection method of the melt level and detection device of the present invention, the porosity of the solid packing layer is calculated at the end of the melt discharge, and the melt level is detected using the porosity. Therefore, the melt level can be detected with high accuracy based on the residual amount of melt. As a result, operation based on the melt level can be performed with high precision, avoiding vertical furnace malfunctions compared to the past, and achieving stable vertical furnace operation. Attached Figure Description

[0033] Figure 1 This is a schematic cross-sectional view of the area near the bottom of the blast furnace.

[0034] Figure 2 This is a schematic cross-sectional view of the blast furnace near the bottom at the end of the discharge process.

[0035] Figure 3 This is a block diagram of a liquid level detection device.

[0036] Figure 4 This is a graph illustrating the results of the embodiment. Detailed Implementation

[0037] The present invention will now be described through embodiments thereof. In this embodiment, a blast furnace is used as a vertical furnace, and an embodiment of a method and apparatus for detecting the liquid level of the molten material in the blast furnace will be described. However, the method and apparatus for detecting the liquid level of the molten material involved in the present invention are not limited to blast furnaces; any vertical furnace in which iron source raw materials and coke are charged into the furnace from the top, oxygen-containing gas is blown into the furnace from the bottom to produce the molten material, and the molten material is discharged from the tap hole can be used.

[0038] Figure 1 This is a cross-sectional schematic diagram of the area near the bottom of the blast furnace 20. Iron ore and coke, serving as raw materials, are alternately and layeredly charged into the furnace body 10 from the top of the blast furnace 20. Hot air containing oxygen and reducing materials such as pulverized coal are blown in from the tuyeres 12 located at the bottom of the furnace body 10. The carbon contained in the coke and pulverized coal is burned by the oxygen-containing gas blown in from the tuyeres 12, thereby generating a high-temperature reducing gas. The iron ore is melted and reduced by this high-temperature reducing gas to produce molten iron. The high-temperature reducing gas used in the melting and reduction of the iron ore is then discharged from the top of the furnace as top gas. The produced molten iron and the slag generated during the production of molten iron accumulate at the bottom of the furnace and are discharged from the taphole 18 at predetermined intervals. In this embodiment, the molten iron and slag are collectively referred to as melt 16. Iron ore is an example of an iron source raw material.

[0039] A solid filling structure 14, filled with coke charged from the top of the furnace, is formed at the bottom of the furnace body 10. Molten material 16 accumulated at the bottom of the furnace body 10 fills the gaps in this solid filling structure 14. When molten material 16 is discharged from the tap hole 18, if the discharge rate from the tap hole 18 is faster than the production rate of molten material 16, the amount of molten material 16 remaining at the bottom of the furnace gradually decreases. If the amount of molten material 16 remaining decreases and the liquid level of molten material 16 drops to the same height as the tap hole 18, high-temperature reducing gas begins to be ejected from the furnace. If high-temperature reducing gas begins to be ejected from the tap hole 18, it becomes difficult to discharge molten material 16 from the tap hole 18. Therefore, other tap holes are opened and the tap hole 18 from which high-temperature reducing gas begins to be ejected is closed, thereby allowing molten material 16 to be continuously discharged from the furnace body 10.

[0040] Figure 2 This is a schematic cross-sectional view of the area near the bottom of blast furnace 20 at the end of the discharge process. (Example) Figure 2 As shown, due to the flow resistance caused by the solid filling structure 14 and the viscosity of the molten material 16, a pressure difference is generated on the upstream and downstream sides of the molten material stream, causing it to tilt towards the tap hole 18. In the molten material level detection method and apparatus of this embodiment, the porosity of the solid filling structure at the bottom of the furnace is calculated based on the tilt angle of the molten material 16 at the end of its discharge, and the molten material level of the molten material 16 at the end of its discharge is detected using this porosity. Thus, by calculating the porosity of the solid filling structure at the end of the discharge of the molten material 16, the molten material level can be detected with high accuracy.

[0041] exist Figure 3 The structure of the molten material level detection device 30 according to this embodiment is shown. Figure 3 As shown, the molten material level detection device 30 includes a level detection unit 31 that calculates the porosity of the solid filling structure 14 and detects the level of the molten material 16 after discharge. The level detection unit 31 is composed of a general-purpose computer including a CPU (central processing unit) for processing information and a storage device, and performs the calculations described later. The molten material level detection device 30 also includes a database 32 pre-stored with various values ​​used in the calculations described later.

[0042] The method for detecting the level of the melt 16 after discharge, performed by the level detection unit 31 of the melt level detection device 30, will be described below.

[0043] The height difference Z between the tapping hole 18 and the liquid level Z of the molten material 16 at the end of tapping. f Furnace bed diameter D h The following equation (1) holds true for the tilt angle θ of the liquid surface of the melt 16.

[0044] [Number 1]

[0045]

[0046] In equation (1) above, Z f It is the height difference (m) between the tap hole 18 and the liquid level Z of the molten material 16 at the end of discharge. k is an experimentally determined dimensionless arbitrary constant (-). The dimensionless arbitrary constant k is determined by the method described in Non-Patent Document 4. For example, in the case of a typical blast furnace, k = 7.0. D h ρ is the furnace bed diameter (m). μ is the viscosity of melt 16 (Pa·s). ρ is the density of melt 16 (kg / m³). 3g is the acceleration due to gravity (9.8 m / s²). 2 ). dp is the particle size (m) of the solid-filled structure 14. ε is the porosity (-) of the solid-filled structure 14. f It is the discharge velocity (m) of the melt 16 at the end of the discharge process. 3 / sec). S is the cross-sectional area of ​​the furnace bed (m²). 2 It should be noted that (-) means dimensionless.

[0047] The liquid level height Z of the melt 16 is determined by the following equation (2).

[0048] [Number 2]

[0049]

[0050] In equation (2) above, Z is the liquid level height of melt 16 (m). V is the amount of melt 16 (kg). ρ is the density of melt 16 (g / m³). 3 S is the cross-sectional area of ​​the furnace bed (m²). 2 ). ε ave It is the average porosity (-) of the solid-filled structure 14.

[0051] The viscosity μ and density ρ of the molten material 16 are the viscosity and density of molten iron and slag, but in this embodiment, the density and viscosity of slag, which has high viscosity and a large impact on pressure loss, are used. The viscosity μ of the molten material 16 can be a constant value (0.25 to 0.35 Pa·s), but it can also be calculated using the method described in Non-Patent Document 1, which calculates based on the component concentrations of CaO, MgO, Al2O3, SiO2, FeO, etc., and temperature. Furthermore, when estimating the viscosity of the molten material using the method described in Non-Patent Document 1, the temperature of the molten material can be a value obtained by measuring the temperature of the discharged molten material using a thermometer 41 such as a thermocouple. The density ρ of the molten material 16 can be a constant value (a past empirical value), but it can also be calculated using the method described in Non-Patent Document 2, which uses the weight ratio of FeO in the molten slag.

[0052] The particle size d of solid-filled structure 14 p When coke is charged from the top of a vertical furnace, the average particle size of the coke charged from the top can be used. Alternatively, as described in Non-Patent Document 3, a coke particle size that takes into account the initial particle size distribution of the coke charged from the top of the furnace and the changes in particle size distribution due to chemical reactions, physical impacts, etc., before the coke descends to the bottom of the furnace can be used. The hearth cross-sectional area S is calculated based on the bottom diameter of the vertical furnace. The average porosity ε is... ave When the liquid level is first detected, the initial value of the porosity ε is 0.4, and thereafter the porosity calculated using the above formula (1) is used.

[0053] Next, the discharge rate v of the melt 16 at the end of the discharge process will be explained. f The calculation method. The discharge velocity v of the melt 16 at the end of discharge. f The following equation (3) is used to obtain it.

[0054] [Number 3]

[0055] v=v0+a×t…(3)

[0056] In equation (3) above, v is the discharge velocity (m) of the melt 16. 3 / sec). v0 is the initial discharge velocity of melt 16 (m). 3 / sec). t is the discharge time (sec). a is the discharge acceleration (m). 3 / sec 2 Thus, in this embodiment, the discharge rate v of the melt 16 is... f It was calculated using the discharge acceleration a, discharge time t, and initial discharge velocity v0 of the melt 16.

[0057] In addition, the amount of melt discharged at discharge time T, M (kg), is calculated by the following formula (4).

[0058]

[0059] In equation (4) above, M is the discharge rate (kg) of melt 16. T is the discharge time (sec). a is the discharge acceleration (m). 3 / sec 2 v0 is the initial discharge velocity (m). 3 / sec). ρ is the density of melt 16 (kg / m³). 3 ).

[0060] Next, the method for calculating the initial discharge velocity v0 in equation (4) above will be explained. According to Bernoulli's law, the pressure loss calculated based on the difference between the energy of the molten material 16 near the tap hole and the energy of the discharged molten material 16, and the pressure loss inside the tap hole calculated according to the Darcy-Weisbach formula are obtained respectively. Assuming that these pressure losses are equal, the following equation (5) is derived.

[0061] [Number 5]

[0062]

[0063] In equation (5) above, P i-Ο ρ is the pressure difference (atm) between the furnace pressure and atmospheric pressure in the vertical furnace. ρ is the density (kg / m³) of the molten material. 3 g is the acceleration due to gravity (9.8 m / sec).2 Z S It is the difference (m) between the height of the molten material 16 at the start of discharge and the height at the outlet side of the tap hole 18. th λ is the diameter (m) of the tap hole 18. λ is the coefficient of friction (-) of the inner wall of the tap hole 18. th This is the depth of the tap hole (m). The tap hole depth is the length (m) of refractory material that the molten material 16 passes through when it exits the tap hole 18. v0 is the initial discharge velocity (m). 3 / sec).

[0064] The friction coefficient λ of the inner wall of the iron outlet hole 18 is obtained by the Swamee-Jain formula and by the following equation (6).

[0065] [Number 6]

[0066]

[0067] In equation (6) above, λ is the coefficient of friction (-) of the inner wall of the tap hole 18. e is the roughness (m) of the inner wall of the tap hole. th ρ is the diameter (m) of the tap hole 18. ρ is the density (kg / m³) of the molten material 16. 3 v0 is the initial discharge velocity (m). 3 / sec). S dh 1 is the cross-sectional area of ​​the tap hole 18. μ is the viscosity (Pa·s) of the molten material 16.

[0068] The pressure inside the vertical furnace is determined by a pressure gauge 42 installed inside the tuyeres 12. Atmospheric pressure can be used as a general value. The height of the molten material 16 at the start of discharge is determined by substituting the residual amount V of the molten material 16 at the start of discharge into equation (2) above. It should be noted that the height of the molten material 16 at the start of discharge is calculated by substituting the initial residual amount V0 into equation (2) above. The molten material 16 inside the blast furnace is generally considered to be pushed upward 1-2m from the tap hole. Therefore, the initial residual amount V0 is calculated based on the capacity of the furnace body 10 so that the height of the molten material 16 is 1-2m above the tap hole. The height of the outlet side of the tap hole 18 is determined by measuring the position of the tap hole 18. The tap hole 18 is drilled using a drill bit, therefore the diameter d of the tap hole 18 is... th The depth L of the extraction hole is determined by measuring the diameter of the drill bit. th The result is obtained by measuring the penetration length of the drill bit when the iron hole 18 is opened.

[0069] The roughness *e* of the inner wall of the tapping hole varies depending on the drilling method, the clay material, and the time elapsed since tapping begins, but operational analysis has confirmed that a value within the range of 0.0001–0.01 μm is appropriate. The cross-sectional area *S* of the tapping hole 18... dhUse the diameter d of the iron tapping hole 18 th The following equation (7) is used to obtain the result.

[0070] S dh =(d th / 2) 2 ×π…(7)

[0071] By solving equations (5) and (6) above, the initial discharge velocity v0 can be obtained. Using v0, the measured value of the discharge volume M of the melt 16 as measured by the discharge volume measuring device 43, the measured value of the discharge time T of the melt 16 as measured by the discharge time measuring device 44, and equation (4) above, the discharge acceleration a can be calculated. If the initial discharge velocity v0 and the discharge acceleration a can be obtained, then the discharge velocity v of the melt 16 can be calculated using equation (3) above. f .

[0072] Furthermore, the residual amount of melt 16 can be calculated by calculating the difference between the amount of melt 16 produced and the amount of melt discharged. Regarding the amount of melt 16 produced, the amount of melt produced can be calculated using the production rate PV of melt 16 calculated using the following formula (8).

[0073] [Number 7]

[0074]

[0075] In equation (8) above, PV is the melting rate (kg / sec). TV is the flow rate of the gas at the furnace top (Nm³). 3 / sec). Fo is the mass concentration of O atoms in the top gas (mol / Nm³). 3 BV is the flow rate (Nm) of the hot air blown in from vent 12. 3 / sec). E O M is the volume fraction of oxygen in the hot air (-). OM(-) is the ratio of the number of oxygen atoms per 1 mol of the target substance in the raw material to the number of metal atoms. M It is the atomic weight (g / mol) of a metal atom.

[0076] The flow rate TV of the gas at the top of the furnace is calculated by the following equation (9).

[0077] TV = BV × E N / F N …(9)

[0078] In equation (9) above, TV is the flow rate of the gas at the furnace top (Nm³). 3 / sec). BV is the flow rate of hot air blown in from vent 12 (Nm³). 3 / sec). E NThis is the volume fraction of nitrogen in the hot air (-). F N It is the volume fraction of nitrogen in the gas at the furnace top (-).

[0079] Mass concentration F of O atoms in the gas at the furnace top O and the volume fraction of nitrogen F N The flow rate BV of the hot air blown in from all the tuyeres 12 is determined by analyzing the gas at the top of the furnace using a gas analyzer 45 via gas chromatography and infrared spectroscopy. The flow rate BV of the hot air blown in from all the tuyeres 12 is determined by a flow meter 46 installed at each tuyere 12.

[0080] The volume fraction of oxygen in hot air, E O The volume fraction of nitrogen E in the hot air can be calculated using the following equation (10). N It can be calculated using the following formula (11).

[0081] E O =(X×0.21+Y) / (X+Y)…(10)

[0082] E N =(X×0.79) / (X+Y)…(11)

[0083] In equations (10) and (11) above, X is the air inlet flow rate (Nm³). 3 / sec). Y is the oxygen blowing flow rate (Nm³). 3 / sec).

[0084] Alternatively, the humidity in the air can be considered, along with the volume fraction of oxygen E in the hot air. O and the volume fraction of nitrogen E in hot air N The following formulas (12) and (13) are used to calculate it.

[0085] E O =(X×0.21+Y) / [X+Y+X×(Z / 18)×22.4]…(12)

[0086] E N =(X×0.79) / [X+Y+X×(Z / 18)×22.4]…(13)

[0087] In equations (12) and (13) above, X is the air inflow rate (Nm³). 3 / sec). Y is the oxygen blowing flow rate (Nm³). 3 / sec). Z is the moisture content of the air (kg / m³). 3 The humidity Z in the air is determined by measuring the air using a hygrometer 47.

[0088] Regarding the ratio OM of the number of oxygen atoms per mol of the target substance to the number of metal atoms in the raw material, the composition concentration of the raw material is determined by chemical analysis, and the ratio OM is calculated based on this composition concentration. The melt 16 is composed of a mixture of molten metal and slag. Therefore, it is preferable to add the slag production rate to the production rate PV of the melt 16 calculated by the above equation (8). In this case, the slag production rate is obtained by calculating the mass ratio of molten oxide to molten metal based on the composition concentration of the raw material and multiplying this mass ratio by the production rate of the molten metal.

[0089] The discharge rate v of the molten material 16 is calculated using equation (3) above. Based on the difference between the production rate PV of the molten material 16 and the discharge rate v of the molten material 16, the residual amount of molten material 16 accumulated at the bottom of the furnace body 10 can be detected. Specifically, the residual amount of molten material 16 at any time t (sec) is detected using equation (14) below.

[0090] [Number 8]

[0091]

[0092] In equation (14) above, V is the residual amount of melt 16 (kg). V0 is the initial residual amount of melt 16 (kg). PV is the manufacturing rate of melt 16 (kg / sec). v is the discharge rate of melt 16 (m). 3 / sec). ρ is the density of melt 16 (kg / m³). 3 The initial residual amount V0 is a constant value set according to the capacity of the furnace body 10. As mentioned above, the molten material 16 in the blast furnace is generally considered to have moved upward 1-2m from the tap hole. Therefore, the initial residual amount V0 is set according to the capacity of the furnace body 10 so that the height of the molten material 16 is 1-2m above the tap hole. By using the above equation (12), the residual amount V of the molten material 16 at any time t (sec) can be detected.

[0093] Thus, in the molten material level detection method and apparatus of this embodiment, the porosity of the solid packing layer is calculated at the end of molten material discharge, and the molten material level is detected using this porosity. Therefore, the molten material level can be detected with high accuracy based on the residual amount of molten material. As a result, operation based on the molten material level can be performed with high precision, thus avoiding vertical furnace malfunctions compared to conventional methods and achieving stable vertical furnace operation.

[0094] Furthermore, if the liquid level of the molten material 16 detected using the above formula (2) exceeds a predetermined threshold, it is preferable to perform an operation that reduces the production speed of the molten material 16. This prevents the liquid level of the molten material 16 from becoming excessively high, thus avoiding problems such as deterioration of gas permeability and tuyer blockage caused by slag. Reducing the production speed of the molten material 16 can be achieved, for example, by reducing the amount of hot air blown in from the tuyer 12. Alternatively, instead of reducing the production speed of the molten material 16, an operation that increases the discharge speed of the molten material 16 can be performed in conjunction with the operation that reduces the production speed of the molten material 16.

[0095] In the above example, a method for determining the residual amount of molten material 16 using the molten material production rate PV, the molten material discharge rate v, and the above equation (14) was explained, but it is not limited to this. The production amount of molten material 16 can also be calculated based on the amount of raw material charged from the top of the furnace and the composition concentration of the raw material. In addition, the discharge amount of molten material 16 can also be calculated by measuring the weight change of the torpedo car containing the molten iron and the amount of slag produced from the slag. Furthermore, the residual amount of molten material 16 can be calculated by taking the difference between the production amount of molten material 16 and the discharge amount of molten material 16.

[0096] Furthermore, the method and apparatus for detecting the liquid level of the molten material described above can be partially modified, and are not limited to blast furnaces or vertical furnaces, to detect the liquid level of liquid contained in all containers that have formed a solid filling structure inside. That is, it is possible to detect the liquid level of liquid remaining at the bottom of the container after liquid contained in the container in a state of immersion into at least a portion of the voids of the solid filling structure has been discharged from the discharge hole provided at the bottom of the container.

[0097] Specifically, the liquid level detection device 30 of this embodiment calculates the porosity of the solid filling structure using the same method as the liquid level detection device 30 for the molten material described above. Furthermore, the calculated porosity and the amount of liquid remaining after discharge are used to detect the liquid level after discharge.

[0098] The liquid level detection method and device involved in this embodiment are not limited to blast furnace processes, but can be applied to all processes in which a liquid is contained in a state of immersion into at least a portion of the voids of the solid filling structure in all containers in which a solid filling structure is formed inside.

[0099] Example

[0100] Next, an embodiment will be described. In this embodiment, the tilt angle of the melt is calculated based on the amount of melt remaining at the end of each melt discharge, and the average porosity ε of the solid-filled structure is calculated based on this tilt angle. aveThe residual amount of molten material was calculated at the end of molten material discharge using the operating conditions during blast furnace operation, various measured values, and the above equation (14). Furthermore, the residual amount of molten material and the calculated average porosity ε were used... ave The liquid level of the molten material was measured. On the other hand, in the comparative example, the porosity was fixed at 0.42, and the liquid level of the molten material was measured using this porosity and the aforementioned residual amount of molten material.

[0101] The residual amount of the above-mentioned molten material was detected, and the ventilation resistance index K in blast furnace operation was calculated. The ventilation resistance index K is a general index used to evaluate the ventilation performance of a vertical furnace, and is calculated by the following equation (15).

[0102] [Number 9]

[0103]

[0104] In the above equation (15), P b This is the air supply pressure (atm) of the hot air blown in from the vent. P t This is the exhaust pressure of the gas at the furnace top (atm). BV is the air volume (Nm³) of hot air supplied from all the tuyeres. 3 / sec).

[0105] Ventilation drag index ratio K r The average ventilation resistance index of the vertical furnace being considered is set as K. ave The value is calculated using the following formula (16).

[0106] [Number 10]

[0107]

[0108] Figure 4 This is a graph illustrating the results of the embodiment. Figure 4 (a) shows the average porosity ε ave The variation of (-). Average porosity ε ave (-) is the 1-day moving average of ε. Figure 4 (b) shows the residual amount of melt (m) 3 Changes in ). Figure 4 (c) Shows the variation in the liquid level (m) of the melt; the white squares are plotted using... Figure 4 (a) shows the liquid level height detected using the porosity shown, which is an example of the invention. The black square plotted points represent the liquid level height detected using a porosity of 0.42, which is a comparative example. Furthermore, Figure 4(c) The dashed line represents the managed value for the molten material level, and the dotted line represents the height of the duct. That is, in order to prevent the molten material level from reaching the duct position, the managed value for the molten material level is a position lower than the height of the duct. Figure 4 (d) shows the variation of the ventilation resistance index ratio (-).

[0109] like Figure 4 As shown in (a), the porosity of the solid-filled structure continuously decreased until 30 hours later, and then increased. This decrease in porosity is reflected in the height of the melt level. Figure 4 In (c), the following was used Figure 4 (a) The white square plot of the invention example with a porosity higher than the black square plot of the comparative example, which kept the porosity constant at 0.42. As a result, for the white square plot, the molten material level exceeded the control value after 18 hours, thus an operation was performed to reduce the molten iron production rate. Consequently, after 20 hours, the residual amount of molten material began to decrease, and the molten material level correspondingly decreased.

[0110] like Figure 4 As shown in (d), the ventilation resistance index ratio increases with the increase of molten material quantity and molten material level. An increase in the ventilation resistance index ratio indicates a decrease in furnace ventilation; therefore, if the ventilation resistance index ratio increases, the blast furnace operation becomes unstable. However, because the amount of molten material was reduced by implementing operations that slowed the iron production rate after 18 hours, the ventilation resistance index ratio also decreased, achieving stable blast furnace operation.

[0111] On the other hand, with the void ratio kept constant (0.42), the residual amount of molten material increases significantly after 18 hours and before 21 hours, and the liquid level of the molten material may reach the tuyeres. Even assuming that the liquid level of the molten material does not reach the tuyeres, the ventilation resistance index ratio increases significantly, and the blast furnace operation becomes unstable, thus failing to achieve stable blast furnace operation.

[0112] Thus, in the molten material level detection method and apparatus according to this embodiment, the porosity of the solid filling structure is calculated at the end of molten material discharge, and the molten material level is detected using this porosity. Therefore, the molten material level can be detected with high accuracy based on the remaining amount of molten material. As a result, it is evident that operational actions based on the molten material level can be performed with high precision, thus avoiding vertical furnace malfunctions compared to conventional methods and achieving stable vertical furnace operation.

[0113] Explanation of reference numerals in the attached figures

[0114] 10 furnace main bodies

[0115] 12 Wind Opportunities

[0116] 14 Solid-filled structure

[0117] 16. Molten material (liquid)

[0118] 18 Iron discharge holes (outlet holes)

[0119] 20 Blast Furnace (Container)

[0120] 30 Liquid level detection device

[0121] 31 Liquid Level Detection Unit

[0122] 32 databases

[0123] 41 Melt thermometer

[0124] 42 air outlet pressure gauge

[0125] 43 Discharge Measurement Instrument

[0126] 44 Discharge Time Measuring Instrument

[0127] 45 Furnace Top Gas Analyzer

[0128] 46 air outlet flow meter

[0129] 47. Hygrometer.

Claims

1. A method for detecting the liquid level of a liquid, comprising detecting the liquid level remaining at the bottom of a container after the liquid contained within the container (which has been filled with a solid filling structure by filling it with a solid material, with at least a portion of the voids in the solid filling structure) has been discharged from a discharge hole located at the bottom of the container, wherein... Calculate the porosity of the solid-filled structure. The calculated porosity and the residual amount of liquid after discharge are used to detect the liquid level after discharge. The porosity of the solid-filled structure is calculated using the inclination angle of the liquid level at the end of the discharge from the discharge orifice.

2. A method for detecting the liquid level height of a molten material, comprising: blowing oxygen-containing gas into the lower part of a vertical furnace, generating high-temperature reducing gas by burning carbon, melting and reducing iron source material loaded from the top of the furnace and forming a solid filling structure within the furnace using the high-temperature reducing gas to produce a molten material, and discharging the molten material through the tap hole of the vertical furnace; and detecting the liquid level height of the molten material remaining at the bottom of the vertical furnace after the discharge of the molten material, wherein... Calculate the porosity of the solid-filled structure. The calculated porosity and the residual amount of the melt after discharge are used to detect the liquid level of the melt after discharge. The porosity of the solid-filled structure is calculated using the inclination angle of the molten surface at the end of the discharge of the molten material from the tap hole.

3. The method for detecting the liquid level height of the molten material according to claim 2, The porosity is calculated using the viscosity of the melt, which is determined based on the component concentration and temperature of the discharged melt.

4. The method for detecting the liquid level height of the melt according to claim 2 or 3, The porosity is calculated using the discharge rate at the end of the discharge of the melt, calculated based on the discharge rate, discharge time, and initial discharge rate of the melt.

5. An operating method for a vertical furnace, If the liquid level height detected by the method for detecting the liquid level height of the melt according to any one of claims 2 to 4 exceeds a predetermined threshold, Perform at least one of the following operations: reducing the manufacturing speed of the molten material and discharging the molten material.

6. A liquid level detection device, comprising detecting the liquid level remaining at the bottom of a container after liquid contained within a container having a solid filling structure formed by filling it with a solid material, with at least a portion of the voids in the solid filling structure being immersed, is discharged from a discharge port provided at the bottom of the container, wherein... The device includes a liquid level detection unit that calculates the porosity of the solid filling structure and uses the calculated porosity and the residual amount of liquid after discharge to detect the liquid level after discharge. The liquid level detection unit uses the tilt angle of the liquid level at the end of the discharge from the discharge hole to calculate the porosity of the solid filling structure.

7. A device for detecting the liquid level of a molten material, comprising: a vertical furnace in which oxygen-containing gas is blown in from the bottom of the furnace, high-temperature reducing gas is generated by burning carbon, iron source material loaded from the top of the furnace and forming a solid filling structure within the furnace is melted and reduced by the high-temperature reducing gas to produce a molten material, and the molten material is discharged from the tap hole of the furnace; the device for detecting the liquid level of the molten material remaining at the bottom of the furnace after the discharge of the molten material. The device includes a liquid level detection unit that calculates the porosity of the solid filling structure and uses the calculated porosity and the residual amount of the molten material after discharge to detect the liquid level of the molten material after discharge. The liquid level detection unit uses the inclination angle of the liquid level of the molten material at the end of the discharge from the iron outlet to calculate the porosity of the solid filling structure.

8. The device for detecting the liquid level of a molten material according to claim 7, The liquid level detection unit calculates the porosity using the viscosity of the melt, which is calculated based on the component concentration and temperature of the discharged melt.

9. The device for detecting the liquid level height of a molten material according to claim 7 or 8. The liquid level detection unit calculates the porosity using the discharge rate at the end of the discharge of the melt, calculated based on the discharge amount, discharge time, and initial discharge rate of the melt.

Images