Method and system for suppressing foaming slag during carbonation of titanium-containing blast furnace slag

Abstract

The present application relates to the technical field of metallurgy, and discloses a method and system for inhibiting foamed slag in a carbonization process of titanium-containing blast furnace slag, the method comprising the following steps: in a normal smelting process of an electric furnace, the thickness of the foamed slag layer is detected in real time; when it is detected that the thickness of the foamed slag layer exceeds a set threshold, an electrode pulsation mode is started; wherein during the electrode pulsation mode, the electrodes of the electric furnace are controlled to reciprocate in the vertical direction; after the electrode pulsation mode ends, a regular electrode control mode is resumed. The present application can effectively reduce the degree of foamed slag, and improve the production capacity and operation stability of the electric furnace.

Description

Technical Field

[0001] This invention relates to the field of metallurgical technology, specifically to a method and system for suppressing foamy slag during the carbonization process of titanium-containing blast furnace slag. Background Technology

[0002] Titanium-containing blast furnace slag is a byproduct of blast furnace ironmaking using vanadium-titanium magnetite, with a TiO2 content typically between 20% and 25%. High-temperature carbonization followed by low-temperature chlorination is currently the most promising industrialization technology for recovering titanium resources from this secondary resource. This process first involves reacting the titanium-containing blast furnace slag with a carbonaceous reducing agent at high temperature in an electric furnace, selectively reducing the titanium oxides in the slag to form titanium carbide (TiC). The resulting carbide slag is then subjected to low-temperature chlorination to produce TiCl4.

[0003] In the actual operation of carbide electric furnaces, a long-standing and unresolved problem is the severe foaming slag phenomenon. When the carbothermic reduction reaction proceeds vigorously, a large number of CO bubbles are generated inside the molten slag. Simultaneously, the TiC particles generated in the reaction have high melting points and high surface activity, easily adsorbing at the gas-liquid interface, significantly reducing the surface tension of the molten slag and increasing the liquid film strength, making it difficult for bubbles to coalesce and break up, leading to a sharp increase in the degree of slag foaming. An excessively thick foaming slag layer can cause a series of problems: reduced effective furnace volume and production capacity, increased electrode consumption, unstable furnace conditions, and in severe cases, slag overflow accidents, forcing the electric furnace to operate at reduced load or even shut down.

[0004] To address this issue, existing technologies have proposed several improvement solutions. For example, patent CN101168801A discloses a reduction carbonization method for titanium-containing raw materials, which controls the reaction rate through a segmented power distribution system to ensure that the thickness of the foamed slag layer does not exceed 50% of the depth of the molten pool. Patent CN114875225A proposes adding slag conditioners such as calcium fluoride to reduce the viscosity and surface tension of the molten slag and improve the degree of foaming.

[0005] However, these methods all fall under the categories of "passive adaptation" or "reaction control," either reducing the foaming tendency by altering the intrinsic properties of the slag or decreasing the gas supply by controlling the reaction rate, but they fail to actively intervene in the conditions for the stable existence of the foam layer. When raw material fluctuations or process parameters deviate, the foam slag problem will still recur. Summary of the Invention

[0006] The main objective of this invention is to provide a method and system for suppressing foamy slag during the carbonization process of titanium-containing blast furnace slag, so as to solve the technical problem of how to actively and effectively suppress foamy slag during the carbonization process of titanium-containing blast furnace slag.

[0007] According to one aspect of the present invention, a method for suppressing foamy slag during the carbonization process of titanium-containing blast furnace slag is proposed. The carbonization process is carried out in an electric furnace, and the method includes the following steps: during the normal smelting process of the electric furnace, the thickness of the foamy slag layer is detected in real time; when the thickness of the foamy slag layer exceeds a set threshold, an electrode pulsation mode is activated; wherein during the electrode pulsation mode, the electrodes of the electric furnace are controlled to reciprocate in the vertical direction; and when the electrode pulsation mode ends, the normal electrode control mode is restored.

[0008] According to one embodiment of the present invention, during the electrode pulsation mode, the amplitude of the reciprocating motion of the control electrode is 20% to 40% of the thickness of the foam slag layer, the frequency is 0.1 to 0.5 Hz, and the duration is 1 to 3 minutes.

[0009] According to one embodiment of the present invention, the amplitude of the reciprocating motion of the electrode is based on the initial position of the working end of the electrode, and the upward and downward motion amplitudes are the same.

[0010] According to one embodiment of the present invention, the threshold is set to 35% to 45% of the molten pool depth.

[0011] According to one embodiment of the present invention, the electric furnace is kept powered during the electrode pulsation mode.

[0012] According to one embodiment of the invention, during electrode pulsation mode, inert gas and / or defoaming agent are sprayed onto the surface of the foam residue layer.

[0013] According to one embodiment of the present invention, the inert gas injection flow rate is 0.5–1.5 Nm³. 3 / h, inert gases include nitrogen and / or argon.

[0014] According to one embodiment of the present invention, the defoamer includes one or more of alumina, magnesium oxide, and calcium fluoride, the particle size of the defoamer is 0.1 to 0.3 mm, and the injection rate is 0.2 to 1.0 kg per ton of slag.

[0015] According to another aspect of the present invention, a system for suppressing foamy slag during the carbonization process of titanium-containing blast furnace slag is proposed. The carbonization process is carried out in an electric furnace. The system includes: a foamy slag thickness detection device configured to detect the thickness of the foamy slag layer in real time during the normal smelting process of the electric furnace; and a control device communicatively connected to the foamy slag thickness detection device and configured to: activate an electrode pulsation mode when the foamy slag thickness detection device detects that the thickness of the foamy slag layer exceeds a set threshold; wherein during the electrode pulsation mode, the electrodes of the electric furnace are controlled to reciprocate in the vertical direction; and when the electrode pulsation mode ends, the normal electrode control mode is restored.

[0016] According to one embodiment of the present invention, the system further includes a blowing device; the control device is configured to control the blowing device to blow inert gas and / or blow defoamer onto the surface of the foam slag layer during electrode pulsation mode.

[0017] In the technical solution of this invention, the electrodes of the carbonization electric furnace are used to actively disrupt the stability conditions of the foam layer through a specific mechanical disturbance method, so as to suppress foam slag without changing the thermodynamic and kinetic conditions of the main reaction, thus ensuring carbonization efficiency and production capacity. Attached Figure Description

[0018] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0019] Figure 1 A flowchart illustrating a method for suppressing foamy slag during the carbonization process of titanium-containing blast furnace slag according to an embodiment of the present invention; Figure 2 A schematic diagram of a foam slag suppression system during the carbonization process of titanium-containing blast furnace slag according to an embodiment of the present invention is shown. Detailed Implementation

[0020] To make the objectives, technical solutions, and advantages of the present invention clearer, the embodiments of the present invention will be further described in detail below with reference to specific examples and the accompanying drawings.

[0021] It should be noted that all uses of "first" and "second" in the embodiments of the present invention are for the purpose of distinguishing two entities or parameters with the same name but different names. It is clear that "first" and "second" are only for the convenience of expression and should not be construed as limiting the embodiments of the present invention. Subsequent embodiments will not explain this in detail.

[0022] refer to Figure 1 This invention proposes a method for suppressing foamy slag during the carbonization process of titanium-containing blast furnace slag. The carbonization process is carried out in an electric furnace, and the method includes the following steps: S1, during the normal smelting process of the electric furnace, the thickness of the foam slag layer is monitored in real time; S2, when the thickness of the foam slag layer exceeds the set threshold, the electrode pulsation mode is activated; during the electrode pulsation mode, the electrodes of the electric furnace are controlled to reciprocate in the vertical direction. S3: After the electrode pulsation mode ends, the electrode normal control mode is restored, completing one operation cycle.

[0023] In embodiments of the present invention, the electrode can be a three-phase graphite electrode. The vertical direction can be perpendicular to the molten pool surface, corresponding to the axial or height direction of the electric furnace. The thickness of the foamed slag layer can be detected in real time by a foamed slag layer thickness detection device, and the control device switches the control mode based on the detection results of the foamed slag layer thickness detection device. The foamed slag layer thickness detection device can include at least one of a resistive probe, a laser rangefinder, a millimeter-wave radar thickness gauge, an infrared thermal imaging detection device, and a furnace wall acoustic monitoring device. The control device can include the existing electrode lifting automatic control module and a newly added electrode pulsation control module. That is, the electrode pulsation control module can be integrated into the existing automatic control device of the electric furnace. The electrode pulsation mode can be implemented by modifying the electrode adjustment program in the automatic control device of the electric furnace without adding new hardware.

[0024] To address the long-standing problem of foamy slag in titanium-containing blast furnace slag carburization electric arc furnaces, this invention provides a solution that differs from existing passive control approaches. In this invention, the electric arc furnace's own electrodes are used to actively disrupt the stable structure of the foam layer through mechanical shearing, causing the bubbles to burst. In some embodiments, the method of this invention requires no additional furnace equipment; it can be implemented simply by modifying the electrode control program. This results in low investment, simple operation, and effectively reduces the degree of foamy slag, improving the furnace's capacity and operational stability. The method of this invention is particularly suitable for the process of producing titanium carbide from titanium-containing blast furnace slag using carbothermic reduction in a closed electric arc furnace.

[0025] In some embodiments, during the electrode pulsation mode, the amplitude of the reciprocating motion of the control electrode is 20% to 40% of the thickness of the foam slag layer, the frequency is 0.1 to 0.5 Hz, and the duration is 1 to 3 minutes.

[0026] In some embodiments, the amplitude of the electrode reciprocating motion is based on the initial position of the electrode working end, and the upward and downward motion amplitudes are the same. The electrode working end is the end of the electrode that is inserted into the furnace, contacts the furnace charge, and participates in the arc discharge; it is typically the lower end of the electrode. The initial position of the electrode working end refers to the stable depth position of the electrode working end under normal smelting mode.

[0027] In some embodiments, the threshold is set to 35% to 45% of the molten pool depth.

[0028] In some embodiments, during the electrode pulsation mode, the electric furnace is kept powered on and the power supply is not cut off.

[0029] In some embodiments, during electrode pulsation mode, a trace amount of inert gas is injected into the surface of the foam slag layer to assist in bubble breaking. The injection flow rate of the inert gas can be 0.5–1.5 Nm³. 3 / h, the inert gas may include nitrogen and / or argon.

[0030] In some embodiments, during electrode pulsation mode, a defoaming agent is sprayed onto the surface of the foam slag layer. The defoaming agent may include one or more of alumina, magnesium oxide, and calcium fluoride, and is in the form of a micro powder with a particle size of 0.1 to 0.3 mm, and the spraying amount is 0.2 to 1.0 kg per ton of slag.

[0031] The determination of the key parameters in this invention is based on in-depth analysis of the foam slag formation mechanism and systematic experimental research, specifically as follows: (1) Basis for setting the threshold of foam slag thickness (35% to 45% of the molten pool depth) Statistical analysis of operational data from multiple industrial electric carbide furnaces shows that when the foamed slag layer thickness exceeds 35% of the molten pool depth, there is a significant loss in the effective furnace volume. Increased electrode embedment depth in the foamed layer leads to decreased arc stability, causing the furnace to enter an unstable operating range. When the thickness reaches 45%, without timely intervention, the foamed layer will rapidly grow to over 70% of the molten pool depth within a short period, posing a risk of slag overflow. Using 35%–45% as a trigger threshold allows sufficient time for foam breaking operations while avoiding excessively frequent interventions that could disrupt normal production.

[0032] (2) Basis for setting electrode pulsation amplitude (20% to 40% of the total thickness of the foam layer) The purpose of electrode pulsation is to disrupt the stable structure of the foam layer through mechanical disturbance, while avoiding excessive disturbance that could lead to molten pool splashing or arc extinction. Experimental studies show that the peak strength of the foam layer occurs in the upper-middle region. When the electrode moves upward by 20%–40% of the foam layer thickness, it can effectively shear the stable foam in this region, causing the bubble film to rupture. Moving downward by the same amplitude can compress the bubbles in the lower part of the foam layer and promote their coalescence. When the amplitude is less than 20%, the disturbance energy is insufficient, and the bubble-breaking effect is not obvious; when the amplitude is greater than 40%, the electrode may detach from the foam layer and enter the gas phase, leading to arc interruption and affecting smelting stability.

[0033] (3) Basis for setting electrode pulsation frequency (0.1~0.5Hz) The foam layer exhibits relaxation characteristics in response to mechanical disturbances. Experimental measurements show that the natural rupture frequency of the titanium-containing slag foam layer is approximately 0.1–0.3 Hz. Using a pulsating frequency of 0.1–0.5 Hz can match the natural oscillation frequency of the foam layer, generating a resonant rupture effect. When the frequency is below 0.1 Hz, the number of disturbances per unit time is insufficient, resulting in low rupture efficiency; when the frequency is above 0.5 Hz, the electrode movement is too rapid, and the inertial force of the slag makes it difficult for the disturbance to be effectively transmitted to the depths of the foam layer, and may also exacerbate electrode mechanical wear.

[0034] (4) Basis for setting the duration of pulsation (1-3 minutes) Field tests showed that, at the aforementioned amplitude and frequency, a significant reduction in the foam layer could be observed after one minute of electrode pulsation; 2-3 minutes of continuous pulsation ensured that the foam layer thickness was reduced to below a safe range. A duration exceeding 3 minutes offered limited improvement in foam breaking effect and may even increase the risk of mechanical failure due to frequent electrode movement, slightly affecting smelting thermal efficiency.

[0035] (5) Auxiliary injection parameters (inert gas flow rate 0.5~1.5Nm) 3 The setting basis for (defoamer micro powder particle size 0.1~0.3mm, injection rate 0.2~1.0kg / t slag) is as follows: Inert gas injection is designed to create a micro-airflow that washes over the surface of the foam layer, accelerating bubble bursting. The flow rate is below 0.5 Nm³. 3 At a speed of 1.5 Nm, the airflow penetration is insufficient; above 1.5 Nm 3 A blown-through rate of 0.1-0.3 mm may cause localized bursts in the foam layer, creating gas short circuits and reducing defoaming efficiency. The defoamer powder particle size is selected to ensure effective suspension and penetration of the foam layer in the airflow, while preventing it from escaping with the airflow due to excessively small particle size or falling directly into the molten pool due to excessively large particle size. The injection rate is controlled at 0.2-1.0 kg / t slag, achieving a concentration that effectively reduces surface tension in localized areas of the foam layer, while the overall addition amount is extremely small, not altering the main properties of the molten slag and avoiding the environmental and cost impacts of excessive additives.

[0036] refer to Figure 2 The present invention also proposes a foam slag suppression system 100 during the carbonization process of titanium-containing blast furnace slag, comprising: a foam slag thickness detection device 10, configured to detect the foam slag layer thickness in real time during normal smelting in the electric furnace; and a control device 20, communicatively connected to the foam slag thickness detection device and configured to: activate an electrode pulsation mode when the foam slag thickness detection device detects that the foam slag layer thickness exceeds a set threshold; wherein during the electrode pulsation mode, the electrodes of the electric furnace are controlled to reciprocate in the vertical direction; and when the electrode pulsation mode ends, the normal electrode control mode is restored. The control device 20 can be communicatively connected to an electrode drive mechanism 30 and control the electrode movement by controlling the electrode drive mechanism 30.

[0037] In some embodiments, the suppression system 100 further includes a blowing device 40; the control device 20 is configured to control the blowing device 40 to blow inert gas and / or blow defoamer onto the surface of the foam slag layer during electrode pulsation mode.

[0038] The following description is based on specific embodiments and comparative examples.

[0039] Example 1 An industrial test of the method of this invention was conducted on an industrial carburizing electric furnace (capacity 12.6 MVA, furnace diameter 5 m). The titanium-containing blast furnace slag composition (mass fraction) was: TiO2: 23.5%, CaO: 26.8%, SiO2: 24.2%, Al2O3: 13.5%, MgO: 8.2%. The reducing agent was coke powder, added at 1.2 times the theoretical amount, and the furnace temperature was maintained at 1650–1700℃.

[0040] The online foam slag thickness detection device was set to trigger a threshold of 40% (0.48m) of the molten pool depth (approximately 1.2m). After approximately 90 minutes of reaction, the foam slag thickness was detected to reach 0.52m, exceeding the threshold, and the control device activated the electrode pulsation mode.

[0041] The three-phase graphite electrode is programmed with a pulse command overlaid on the existing automatic control program: the electrode moves upward 0.2m (approximately 40% of the total foam layer thickness of 0.5m) from its initial position, then downward 0.2m, repeating this cycle at a frequency of 0.3Hz for 2 minutes. Throughout the process, the electric furnace maintains normal power supply.

[0042] After the electrode pulsation began, the foam layer inside the furnace was observed to begin to recede significantly within 30 seconds, and the furnace pressure fluctuations decreased. After the pulsation ended, the foam layer thickness dropped to below 0.28 μm, and the control device returned to the conventional electrode control mode. The entire process did not affect the normal operation of the electric furnace, nor did it result in splashing or drastic fluctuations in furnace conditions. Compared with the control furnace that did not use this invention, the reduction and carbonization cycle of this furnace was shortened by 10%, and the power consumption per ton of slag was reduced by 7%.

[0043] Example 2 An experiment was conducted on an electric furnace of the same specifications, employing another embodiment of the method of the present invention: Simultaneously with electrode pulsation, nitrogen-carried alumina micropowder was injected into the surface of the foam layer through nozzles arranged around the furnace cover. The alumina particle size was 0.15–0.25 mm, and the injection flow rate was 1.0 Nm³. 3 / h, injection rate 0.5kg / t slag. Electrode pulsation parameters are adjusted to: amplitude 30% of foam layer thickness, frequency 0.4Hz, duration 1.5 minutes.

[0044] The results showed that the foam layer fell back faster than in Example 1, taking approximately one minute from triggering to falling back to a safe range. Analysis suggests that the impact of alumina micropowder on the bubble film further disrupted foam stability, creating a synergistic bubble-breaking effect with electrode pulsation. The carbonization rate in this batch was 95.2%, comparable to the control batch, indicating that the injection of trace amounts of alumina did not affect the carbonization effect of the main reaction.

[0045] Comparative Example 1 Using the same raw materials and furnace type as in Example 1, only the defoaming agent powder was injected without electrode pulsation. When the foam layer thickness exceeded the threshold, the injection device was activated to inject calcium fluoride powder (particle size 0.1-0.2 mm) into the foam layer at a rate of 0.8 kg / t slag and a flow rate of 1.2 Nm³. 3 The spraying was continued for 3 minutes at a rate of / h. The results showed that the foam layer thickness decreased slightly within 2 minutes, but the decrease was limited (from 0.53m to 0.42m), still exceeding the safety threshold, requiring further spraying. This indicates that simply spraying the micropowder is less effective at breaking bubbles than electrode pulsation, but it can be used as an auxiliary method to enhance the effect.

[0046] Comparative Example 2 Using the same raw materials and furnace type as in Example 1, but without initiating any defoaming measures, the reaction rate was controlled solely by the conventional power distribution system. During operation, the thickness of the foamy slag in the mid-stage of reduction and carbonization continued to increase, reaching a maximum of 75% of the molten pool depth. The electric furnace was forced to operate at a reduced load to control the furnace pressure, extending the smelting cycle by 18% and increasing the power consumption per ton of slag by 11%.

[0047] In summary, to address the severe foamy slag problem caused by the stable bubble film of TiC particles during the carbothermic reduction of titanium-containing blast furnace slag, this invention proposes an active intervention method that utilizes existing graphite electrodes for mechanical disturbance. By controlling the reciprocating motion of the electrodes, foamy slag is suppressed, and the suppression effect is further enhanced by the auxiliary means of injecting inert gas and / or injecting defoaming agents.

[0048] Those skilled in the art should understand that the discussion of any of the above embodiments is merely exemplary and is not intended to imply that the scope of the invention (including the claims) is limited to these examples. Within the framework of the invention, technical features of the above embodiments or different embodiments can be combined, and many other variations of the different aspects of the invention as described above exist, which are not provided in the details for the sake of brevity. Therefore, any omissions, modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the invention should be included within the protection scope of the invention.

Claims

1. A method for suppressing foamy slag during the carbonization process of titanium-containing blast furnace slag, characterized in that, The carbonization process is carried out in an electric furnace, and the method includes the following steps: During the normal smelting process of the electric furnace, the thickness of the foam slag layer is monitored in real time. When the thickness of the foam slag layer exceeds a set threshold, the electrode pulsation mode is activated; during the electrode pulsation mode, the electrodes of the electric furnace are controlled to reciprocate in the vertical direction. After the electrode pulsation mode ends, the electrode normal control mode is restored.

2. The method according to claim 1, characterized in that, During the electrode pulsation mode, the amplitude of the reciprocating motion of the electrode is controlled to be 20% to 40% of the thickness of the foam slag layer, the frequency is 0.1 to 0.5 Hz, and the duration is 1 to 3 minutes.

3. The method according to claim 2, characterized in that, The amplitude of the reciprocating motion of the electrode is based on the initial position of the working end of the electrode, and the upward and downward motion amplitudes are the same.

4. The method according to claim 1, characterized in that, The set threshold is 35% to 45% of the molten pool depth.

5. The method according to claim 1, characterized in that, During the electrode pulsation mode, the electric furnace is kept powered on.

6. The method according to claim 1, characterized in that, During the electrode pulsation mode, inert gas and / or defoaming agent are sprayed onto the surface of the foam residue layer.

7. The method according to claim 6, characterized in that, The inert gas injection flow rate is 0.5–1.5 Nm³. 3 / h, the inert gas includes nitrogen and / or argon.

8. The method according to claim 6, characterized in that, The defoaming agent includes one or more of alumina, magnesium oxide, and calcium fluoride, and the particle size of the defoaming agent is 0.1-0.3 mm, and the injection rate is 0.2-1.0 kg per ton of slag.

9. A system for suppressing foamy slag during the carbonization process of titanium-containing blast furnace slag, characterized in that, The carbonization process is carried out in an electric furnace, and the system includes: A foam slag thickness detection device is configured to detect the thickness of the foam slag layer in real time during the normal smelting process of the electric furnace. The control device is communicatively connected to the foam slag thickness detection device and configured as follows: When the foam slag thickness detection device detects that the foam slag layer thickness exceeds a set threshold, the electrode pulsation mode is activated; wherein during the electrode pulsation mode, the electrodes of the electric furnace are controlled to reciprocate in the vertical direction. After the electrode pulsation mode ends, the electrode normal control mode is restored.

10. The system according to claim 9, characterized in that, It also includes a blowing device; the control device is configured to control the blowing device to blow inert gas and / or blow defoamer onto the surface of the foam slag layer during the electrode pulsation mode.

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