A method of detecting melt level in a smelting furnace

Abstract

The application discloses a method for automatically detecting the height of a melt pool of a smelting furnace, and belongs to the technical field of metallurgical automatic detection. In view of the problems of large detection error and high safety risk of traditional manual detection, the application drives a detection rod to uniformly descend at a constant speed through a hoisting device, uses a torque sensor to monitor the upward force suffered by the detection rod in the melt in real time, combines the length of the wire rope, and accurately positions the interfaces of the medium layers according to the mechanical characteristics that the force of the slag layer changes linearly and the forces of the sticky slag layer and the matte layer change nonlinearly, so as to automatically calculate the thicknesses of the slag layer, the sticky slag layer, the matte layer and the frozen layer at the bottom of the furnace. When the detection rod touches the bottom and the tension disappears, the system is automatically stopped and reversely recovered, and after the adhesive cools down, the system is automatically vibrated to fall and complete zero calibration, and meanwhile, the reference deviation caused by the burning loss of the detection rod is compensated through a visual and weight detection device. The application realizes fully-automatic and high-precision detection, eliminates the risk of scalding, reduces the labor intensity of the post, and provides reliable data support for accurate regulation and control of the furnace condition.

Description

Technical Field

[0001] This invention relates to the field of metallurgical automation testing technology, specifically to a technology for detecting the height of melt in a molten pool furnace, and in particular to an automatic detection method capable of automatically and accurately measuring the thickness of the slag layer, the slag-adhering layer, the matte layer, and the frozen layer at the bottom of the furnace. Background Technology

[0002] In the pyrometallurgical production process, the height and thickness distribution of the melt (usually divided into a frozen layer, matte layer, slag layer and slag layer from bottom to top) in the molten pool furnace are key process parameters for judging the furnace operating status, controlling the smelting reaction effect and adjusting the material and fuel ratio.

[0003] Currently, the metallurgical industry commonly uses manual measurement to obtain molten metal height data. The specific procedure is as follows: operators use hoists or electric hoists to slowly lower a measuring tool (usually made of round steel) through a pre-drilled hole in the furnace top into the molten metal until it touches the furnace bottom. After a specified period of time, the measuring tool is removed from the furnace, and the interface height of the slag layer, slag-adhering layer, and matte layer is roughly estimated by manually measuring the adhesive material of different locations and thicknesses on the measuring tool's surface.

[0004] However, this traditional manual measurement method has the following significant drawbacks: (1) The measurement error is large and highly subjective. When the smelting reaction effect is poor and the slag-matte separation is incomplete, a layer of slag-matte mixture will form in the furnace. The interface between the layers is distinguished by visually observing the adhesive on the gauge. This is highly dependent on the experience of the operators. The interface is vague, which leads to a large deviation in the measurement results and makes it difficult to meet the process requirements of precise control in modern smelting.

[0005] (2) Significant safety hazards. The measuring hole is usually located in the high-temperature zone of the furnace. When measuring personnel are operating, they need to be in close contact with the high-temperature molten material and the hot flue gas escaping from the top of the furnace, which can easily lead to safety accidents such as burns and scalds. At the same time, there is a risk of mechanical injury during the hoisting operation, and the inherent safety is low.

[0006] (3) Frequent equipment failures. When operating the hoist manually, it is difficult to accurately control the timing of lowering and stopping. If the operator does not stop lowering the wire rope in time after the gauge reaches the bottom of the furnace, it is very easy to cause the wire rope to become excessively slack, which can lead to the wire rope coming off the groove, getting stuck, or even burning the gauge due to prolonged exposure to the high-temperature molten metal. This not only leads to single measurement failures, but also seriously affects the continuity of normal production and the real-time control of the furnace condition.

[0007] (4) Harsh working environment. The gauging hole on the top of the furnace is constantly filled with smoke and dust. Operators work in a high-temperature environment containing sulfides or metal dust for a long time, which causes great damage to their physical and mental health.

[0008] In conclusion, traditional manual methods for detecting melt height can no longer meet the demands of modern metallurgical industries for safe, efficient, and intelligent production. Therefore, there is an urgent need to develop an automated melt height detection method that can replace manual operation and achieve automatic measurement and accurate feedback. Summary of the Invention

[0009] This invention aims to overcome the shortcomings of existing methods for manually detecting melt height in molten pool smelting furnaces, such as large measurement errors, significant safety hazards, equipment vulnerability, and harsh working environments. It provides an automated method for detecting melt height in molten pool smelting furnaces. This method achieves full automation from lowering the measuring gauge, force monitoring, interface positioning, automatic stop upon bottoming, automatic cleaning, to self-inspection, thereby improving the intelligent control level and inherent safety of the smelting process.

[0010] To achieve the above objectives, the present invention provides the following technical solution: A method for automatically detecting the height of melt in a molten pool melting furnace includes the following steps: The hoisting device is activated to drive the measuring rod to descend at a constant speed from the measuring rod hole at the top of the furnace. During the descent, the upward force on the measuring rod is monitored in real time by a torque sensor connected to the measuring rod. Based on the force changes, combined with a counting / measuring device that measures the length of the wire rope, the interface height at which the measuring rod enters the melt layer with different densities and viscosities is determined. When the measuring rod enters the slag layer, the force changes linearly; when it enters the slag-adhered layer or matte layer, the force changes non-linearly. The corresponding melt interface height is determined based on the critical position of the non-linear force change. When the measuring rod descends to the bottom of the furnace, the hoisting device automatically stops descending and reverses to lift the measuring rod back to the initial position. After the measuring rod is lifted to the initial position, it is left to stand for a predetermined time to allow the melt adhering to the measuring rod surface to cool and solidify. The cooled adhering material is then shaken off into the furnace. After cleaning, the torque sensor of the system is automatically zeroed and calibrated.

[0011] As a further preferred embodiment of the present invention, the smelting melt is divided into a frozen layer, a matte layer, a slag-adhering layer and a slag layer from bottom to top; in different medium layers, due to differences in density and viscosity, the upward force and overall resultant force on the measuring instrument are different, and the system automatically calculates the height or thickness of each melt layer based on the abrupt change point of the force change.

[0012] As a further preferred embodiment of the present invention, during the uniform descent of the winch device, a counting / measuring device fixed to the side of the winch automatically records the descent length of the wire rope; after the detection program is started, the tension of the wire rope is equal to the weight of the measuring tape.

[0013] As a further preferred embodiment of the present invention, when the measuring rod is lowered to the bottom of the furnace, the system detects that the downward pulling force has automatically disappeared, determines that the measuring rod has reached the bottom of the furnace, and then triggers the hoist to automatically stop and retract, so as to avoid the wire rope being lowered too much, causing rope tangling and measuring rod burnout.

[0014] As a further preferred embodiment of the present invention, a visual positioning device and a weight inspection device are also provided; after the measuring tape is used, the degree of burn-off of the measuring tape is detected by the visual positioning device and the weight inspection device, the system automatically adjusts the initial detection height position according to the actual length of the measuring tape after burn-off, and determines whether the measuring tape needs to be replaced according to the degree of burn-off.

[0015] As a further preferred embodiment of the present invention, the inlet of the measuring hole is provided with a frustum-shaped flared structure that is larger at the top and smaller at the bottom, which is used to guide the measuring rod back into place when the measuring rod shakes, and to make the knocked-off adhesive automatically fall into the furnace.

[0016] As a further preferred embodiment of the present invention, based on the force values ​​of different medium layers displayed by the torque sensor and combined with the descent depth of the gauge, the density values ​​of different molten media can be calculated, and the quality of the slag-matte separation effect can be judged accordingly.

[0017] Compared with the prior art, the present invention has the following outstanding advantages: 1. This invention utilizes a torque sensor to capture the critical position of nonlinear force changes during gauging in real time, which can accurately locate the interface between the slag layer, the slag-adhering layer, the matte layer, and the frozen layer. It can effectively overcome the measurement error caused by manually observing the thickness of the adhering material, especially when the slag-matte separation is unclear, it can still achieve accurate measurement, reducing the requirements for operator experience.

[0018] 2. The present invention eliminates the need for manual contact with the high-temperature areas of the furnace body throughout the entire process. The detection and cleaning are automatically completed through a remote or local control box, which completely avoids the risks of burns, mechanical injuries and other risks that may occur during manual measurement. At the same time, it also eliminates the need for operators to be exposed to high-temperature flue gas and dust environment for a long time.

[0019] 3. This invention automatically determines that the measuring rod has reached the bottom by detecting the disappearance of tension, and automatically stops lowering and retracts it, effectively avoiding equipment accidents such as wire rope derailment, rope breakage, and measuring rod burnout caused by delays due to manual operation.

[0020] 4. This invention features automatic vibration cleaning, automatic zeroing calibration under stress, and dual visual / weight detection of the gauge's burn level. The system can automatically correct the measurement benchmark based on the actual wear of the gauge, providing timely warnings and replacements, effectively extending the equipment's service life and ensuring long-term measurement accuracy. Attached Figure Description

[0021] Figure 1This is a schematic diagram of the structure of an automatic melt height detection device for a molten pool smelting furnace according to the present invention.

[0022] Figure 2 The diagram shows the force analysis of the slag layer density gradient model in this invention, where: (a) is the density distribution of each layer of the smelting melt along the depth; (b) is the curve of the buoyancy of the measuring instrument as a function of the insertion depth; (c) is the curve of the apparent weight (effective gravity) of the measuring instrument as a function of the insertion depth; and (d) is the curve of the rate of change of buoyancy (first derivative) as a function of the insertion depth. Detailed Implementation

[0023] The embodiments of the present invention will now be clearly and completely described in conjunction with the technical principles of the present invention.

[0024] The method for automatically detecting the height of melt in a molten pool smelting furnace proposed in this invention includes the following hardware implementation basis: Figure 1 The diagram shows the winch, measuring rod, torque sensor, counting / measuring device, and the back-end control system. Before measurement begins, the winch adjusts the suspended measuring rod to a fixed "zero position" awaiting instructions. Once the measurement program is initiated, the winch drives the wire rope, lowering the measuring rod at a constant speed from the measuring hole at the top of the furnace into the furnace. During the descent, the torque sensor fixed to the end of the wire rope monitors the upward force acting on the measuring rod in real time, while the counting / measuring device located on the winch side synchronously and continuously records the precise descent length of the wire rope. These two components constitute a real-time correspondence between the measuring rod's spatial coordinates and mechanical parameters.

[0025] The core physical measurement logic of this invention lies in establishing a mapping model between mechanical differentials and medium density by utilizing the different buoyancy or resistance generated by the measuring rod during its uniform descent through melt media of varying densities. Let the cross-sectional area of ​​the measuring rod be A, the current immersion depth be h, and the weight of the measuring rod be G. When the measuring rod is immersed in a homogeneous melt of density ρ, according to Archimedes' principle and force balance, the downward net force F on the wire rope measured by the torque sensor is F = G - ρ × g × A × h. Taking the first derivative of the above equation with respect to the descent displacement h, we obtain dF / dh = -ρ × g × A. Since the gravitational acceleration g and the cross-sectional area A of the measuring rod are constant within a specific stage, the absolute value of the slope of the net force F changing with depth h, k = |dF / dh|, is strictly proportional to the current melt density ρ.

[0026] However, in actual production, especially in nickel pyrometallurgical processes, the molten metal in the hearth is divided into four layers from top to bottom: a slag layer, a slag-adhering layer, a nickel matte layer, and a frozen layer. The key difference is that the slag-adhering layer is not an abrupt interface, but rather a mixed transition layer of molten slag and nickel matte. Its density gradually increases from top to bottom as the slag content decreases and the nickel matte content increases, exhibiting a linear gradient characteristic.

[0027] To accurately locate the interface of this gradient layer, the present invention further constructs a segmented force model. Taking the nickel pyrometallurgical process parameters as an example (as shown in Table 1), the parameters of different medium layers are as follows: Table 1 Medium parameters of each layer In the sticky slag layer, the density function at depth h is linearly graded: , where h1<h ≤ h1+h2, the top density is ρ1 (consistent with the slag layer), and the bottom density is ρ3 (consistent with the nickel matte layer).

[0028] According to Archimedes' principle, buoyancy is equal to the weight of the displaced liquid. Since the density of the sticky slag layer varies, the buoyancy needs to be calculated by integration: , where A is the cross-sectional area of the dipstick, g is the gravitational acceleration, and x is the insertion depth of the dipstick. The segmented calculation is as follows: Section ①: Slag layer (0≤x≤h1) The dipstick is only immersed in the slag layer, with uniform density: F_buoy(x) =ρ 1 g A x The buoyancy increases linearly with depth, and the growth rate is ρ1gA.

[0029] Section ②: Sticky slag gradient layer (h1<x≤h1+h2) The dipstick passes through the slag layer and enters the sticky slag layer, which requires integrating the gradient density: F_buoy(x) = gA·[ρ 1 h 1 +∫(h 1 →x) (ρ 1 + (ρ 3 -ρ 1 )(h-h 1 ) / h 2 ) dh] Integration result: F_buoy(x) = gA·[ρ 1 x + (ρ 3 -ρ 1 )(x-h 1 )² / (2h 2 )] The buoyancy in this segment is a quadratic function (parabola), with a gradually increasing rate of increase and a slope that gradually changes from ρ1gA to ρ3gA.

[0030] Section ③: Nickel matte layer (h1+h2) <x≤h1+h2+h3) The gauge probe penetrated completely through the slag layer and entered the nickel matte layer: F_buoy(x) = gA·[ρ 3 x + (ρ 1 -ρ 3 )h 2 / 2] It reverts to linear growth, with a growth rate of ρ3gA (steeper than the slag layer).

[0031] Section 4: Frozen layer (x>h1+h2+h3) Measurements reached the frozen layer: F_buoy(x) = gA·[ρ 4 x + (ρ 1 -ρ 3 )h 2 / 2 + (ρ 3 -ρ 4 )(h 1 +h 2 +h 3 )] Based on the above piecewise function, the net force (apparent weight) on the measuring instrument is: F(x) = G - F_buoy(x) The total weight of the measuring instrument is: G =ρ 0 g A L Where ρ0 is the density of the material being measured (steel: 7850 kg / m³). 3 ), L is the total length of the measuring instrument.

[0032] Given the characteristics of slag-laden layers, such as gradual density changes and continuous changes in the rate of stress change, traditional threshold judgments based on "stress abrupt change points" may drift. Therefore, this invention optimizes the interface judgment method by introducing the second derivative method: when the gauge enters the slag-laden layer, the rate of density change dρ / dx is a constant positive value; therefore, the second derivative of apparent weight with respect to depth is: It is a non-zero constant (representing a flat slope).

[0033] Slag-slag interface (upper interface): The system detected that the second derivative changed abruptly from zero (within the slag layer) to a non-zero constant; Slag-nickel matte interface (lower interface): The system detected that the second derivative changed from a non-zero constant back to zero.

[0034] By tracking the start and end points of the second derivative, the system can accurately pinpoint the upper and lower boundaries of the slag-adhering layer, and then calculate the actual thickness of the slag layer, the slag-adhering layer, and the nickel matte layer. Simultaneously, for the high-melting-point frozen layer that may form at the furnace bottom during smelting, the system can also accurately measure the thickness of the frozen layer based on the specific resistance signal when the gauge contacts the frozen layer, combined with the height difference during lowering.

[0035] At the end of the detection process, the gauge continues to descend until it reaches the furnace bottom. Once the downward pull disappears instantly, the system immediately determines that the gauge has reached its limit. It then controls the winch to automatically stop lowering and immediately reverse to retrieve the gauge. This prevents the wire rope from becoming excessively slack at the furnace bottom, causing tangling, or the gauge from being burned by prolonged immersion in the high-temperature molten metal. Simultaneously, regarding the high-melting-point frozen layer that may form at the furnace bottom during smelting, the system can accurately measure the thickness of the frozen layer based on the specific contact resistance signal generated when the gauge contacts the frozen layer, combined with the difference in descent height. This provides crucial information for operators to adjust the furnace bottom thermal regime in a timely manner.

[0036] Because the measuring gauge is exposed to high-temperature melt and highly corrosive environments for extended periods, its lower cross-sectional area inevitably thins due to erosion, resulting in a continuous reduction in the cross-sectional area S. Without correction, directly applying the aforementioned differential formula to deduce the density will produce a positive deviation, leading to positioning errors at the medium interface. Therefore, this invention includes an additional visual positioning device and a weight checking device after the measuring gauge is lifted and returned to its original position. The system cross-compares the detection data from these two devices to accurately measure the actual thinning of the measuring gauge's cross-sectional area S due to burning. current It can also calculate the absolute shortening length caused by melting loss during gauging. In subsequent measurements, the system will automatically adjust the corrected S... current By substituting mathematical models for dynamic calibration and automatically compensating for the initial zero-position coordinates, the height measurement drift caused by physical wear and tear on the measuring instrument is completely eliminated. When the residual cross-sectional area or length of the measuring instrument falls below a safety threshold, the system directly issues a replacement warning.

[0037] Once the gauge completes its inspection and is returned to its initial zero position, the system automatically enters the cleaning and self-resetting process. The gauge needs to be left to stand for a preset time to allow the molten material adhering to its surface to cool and solidify. Then, it is directly shaken off the surface material by mechanical tapping or vibration, causing it to fall through the gauge hole and return to the furnace. After the cleaning process is complete, the torque sensor signal automatically performs a zero-stress calibration operation to ensure that the sensor is in an absolutely zero-stress state before each measurement. Furthermore, the control method of this invention has both remote and local control modes: a dedicated control box is configured on-site, allowing personnel to directly start the inspection in local mode; in remote mode, operators in the central control room can remotely send control commands. The system also has a timed self-check function, allowing for the setting of fixed inspection cycles according to actual process requirements, truly achieving unattended, automated, high-precision melt height monitoring.

Claims

1. A method for automatically detecting the height of melt in a molten pool smelting furnace, characterized in that, Includes the following steps: (1) Start the hoisting device and drive the measuring rod to descend at a constant speed from the measuring rod hole on the top of the furnace; (2) During the descent of the measuring tape, the upward force on the measuring tape is monitored in real time by a torque sensor connected to the measuring tape; (3) Based on the force change monitored by the torque sensor, combined with the counting / measuring device for measuring the length of the wire rope, determine the interface height when the gauge enters the melt layer with different densities and viscosities; when the gauge enters the slag layer, the force changes linearly, and when the gauge enters the slag layer or matte layer, the force changes nonlinearly. Determine the corresponding melt interface height based on the critical position of the nonlinear force change. (4) When the gauge descends to the bottom of the furnace, the hoisting device automatically stops lowering and reverses to lift the gauge back to the initial position; (5) After the gauge is lifted to the initial position, it is left to stand for a predetermined time until the melt adhering to the gauge surface cools and solidifies. Then, the cooled adhering material is shaken into the furnace. (6) After cleaning, the torque sensor of the system is automatically calibrated to zero under force.

2. The method for automatically detecting the height of melt in a molten pool smelting furnace according to claim 1, characterized in that: In step (3), the smelting melt is divided into a frozen layer, a matte layer, a slag layer and a slag layer from bottom to top. In different medium layers, due to different densities and viscosities, the upward force and overall resultant force on the measuring instrument are different. The system automatically calculates the height or thickness of each melt layer based on the abrupt change point of the force change.

3. The method for automatically detecting the height of melt in a molten pool smelting furnace according to claim 1, characterized in that: In step (1), during the uniform descent of the winch, the counting / measuring device fixed to the side of the winch automatically records the descent length of the wire rope; after the detection program is started, the tension of the wire rope is equal to the weight of the measuring tape.

4. The method for automatically detecting the height of melt in a molten pool smelting furnace according to claim 1, characterized in that: In step (4), when the measuring rod is lowered to the bottom of the furnace, the system detects that the downward pulling force has automatically disappeared, determines that the measuring rod has reached the bottom of the furnace, and then triggers the hoist to automatically stop and retract, so as to avoid the wire rope being lowered too much and causing the rope to become tangled and the measuring rod to burn.

5. The method for automatically detecting the height of melt in a molten pool smelting furnace according to claim 1, characterized in that: In step (5), the lower part of the measuring instrument is automatically struck by a mechanical hammer, causing the cooled adhesive to vibrate and fall off.

6. The method for automatically detecting the height of melt in a molten pool smelting furnace according to claim 1, characterized in that: It is also equipped with a visual positioning device and a weight inspection device. After the measuring tape is used, the visual positioning device and the weight inspection device detect the degree of burn-off of the measuring tape. The system automatically adjusts the initial detection height position according to the actual length of the measuring tape after burn-off, and determines whether the measuring tape needs to be replaced according to the degree of burn-off.

7. The method for automatically detecting the height of melt in a molten pool smelting furnace according to claim 1, characterized in that: The measuring hole entrance is equipped with a frustum-shaped flared structure that is wider at the top and narrower at the bottom. This structure is used to guide the measuring rod back into place when it shakes and to allow the knocked-off adhesive to fall automatically into the furnace.

8. The method for automatically detecting the height of melt in a molten pool smelting furnace according to claim 1, characterized in that: Based on the force values ​​of different medium layers displayed by the torque sensor, combined with the depth of the gauge descent, the density values ​​of different molten media are calculated, and the quality of slag-matte separation is judged accordingly.

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