In modern steelmaking processes, the baking quality of ladles (containers holding molten steel) and tundishes (connecting ladles and crystallizers) is crucial. Traditional air-assisted baking methods suffer from high energy consumption, low efficiency, uneven baking, and large emissions. Oxygen-enriched and all-oxygen ladle baking devices have emerged, and with their significant technological advantages, they are becoming key equipment for energy saving, emission reduction, quality improvement, and efficiency enhancement in steelmaking processes.

4.1.1. Core Technology of Oxygen-Enriched and All-Oxygen Ladle Baking Devices

1. Oxygen-Enriched Combustion: Increasing the oxygen concentration in the combustion air to above 21% (usually 23%-35%), replacing part of the air.
2. All-Oxygen Combustion: Using high-purity oxygen (usually >90%) to replace air as the oxidant, and the fuel burns in a pure oxygen or oxygen-enriched environment.
3. Optimized Ladle Baking Device Structure: Combining the characteristics of oxygen-enriched/all-oxygen combustion, optimizing burner design (such as high-speed flames, low-NOx burners), flue gas recovery and utilization systems, and intelligent control systems (precise control of temperature curves and atmosphere), etc.

4.1.2. Main Application Scenarios and Advantages

1. Ladle Baking (Core Application):
   • Application Subdivisions:
     1. Baking after Cold Repair: The first high-temperature baking (to ~1200℃ or above) of a newly built or overhauled ladle to thoroughly remove moisture and sinter the refractory material.
     2. Baking after Hot Repair: Rapid restoration of operating temperature after local repair (such as slag line) during turnover.
     3. Insulation Baking during Turnover: Maintaining high temperature (usually >800℃) while the ladle is waiting to receive molten steel to prevent a significant temperature drop.
   • Advantages Deepened:
     1. Ultimate Energy Saving: As mentioned earlier, the energy-saving effect is significant (oxygen-enriched 15-25%, all-oxygen 25-35%+). Key point: The flue gas volume of all-oxygen combustion is extremely small (about 20-25% of air combustion), and the proportion of water vapor in the flue gas is extremely high (up to 70% or more), which makes the flue gas waste heat recovery efficiency extremely high (such as for preheating oxygen or fuel), further amplifying the energy-saving effect.
     2. Revolutionary Improvement in Baking Quality:
        1. Temperature Uniformity: High-speed flames and strong radiant heat transfer significantly improve the axial and radial temperature uniformity of the ladle wall, avoiding local "overburning" (leading to refractory spalling) or "underbaking" (residual moisture leading to molten steel splashing or refractory bursting), significantly reducing thermal shock damage, and extending the life of the lining (usually by 10-20%).
        2. Precise Control of Heating Curve: The intelligent control system, combined with its fast response characteristics, can more accurately execute complex baking curves (such as the low-temperature dehydration stage, medium-temperature de-carbonization stage, and high-temperature sintering stage of cold ladle baking), optimizing the refractory material performance.
     3. Maximizing Turnover Efficiency: Baking time is shortened by 30-50%, meaning that the ladle can be put into use faster for the next time, reducing the number of online ladles required, and improving the utilization rate of a single ladle, especially suitable for high-efficiency continuous casting and fast-paced production.
     4. Molten Steel Quality Assurance:
        1. Reduced Temperature Drop : The uniform high temperature of the lining minimizes heat absorption when molten steel is injected, stabilizing the superheat of the molten steel, which is crucial for smooth continuous casting and billet quality (such as central segregation and internal cracks).
        2. Reduced Nitrogen Increase Risk: All-oxygen combustion basically eliminates the nitrogen in the combustion air, significantly reducing the risk of molten steel absorbing nitrogen from the atmosphere during the empty ladle stage after baking or the initial water injection stage, which is particularly important for the production of ultra-low carbon steel and high nitrogen controlled steel.
     5. Strengthened Environmental Advantages:
        1. Absolute Emission Reduction: The significant reduction in flue gas volume means that the absolute total emissions of particulate matter, SOx (if the fuel contains sulfur), and CO₂ are significantly reduced.
        2. NOx Control: Oxygen-enriched combustion itself inhibits the generation of thermal NOx (no large amount of N₂ in the high-temperature zone). All-oxygen combustion combined with low-NOx burner design (such as staged combustion and flue gas recirculation FGR) can achieve NOx emission concentrations far lower than air combustion.
        3. Low Noise: Compared to the strong jet noise of traditional high-speed burner air combustion, oxygen-enriched/all-oxygen combustion (especially all-oxygen) usually operates more quietly.
2. Tundish Baking (Core Application):
   • Application Subdivisions:
     1. Cold Tundish Baking: Baking to operating temperature (~1100-1200℃) after new construction or long-term disuse.
     2. Hot Turnover Baking: Rapid heating and insulation between consecutive castings.
     3. Baking and Drying Device: Online drying (at lower temperatures) of insulation boards, coatings, etc., used in tundish linings.
   • Advantages Deepened:
     1. 100% Successful Casting Start-up: Rapid and uniform high temperature ensures that the tundish lining and nozzle are fully preheated, eliminating the phenomenon of "cold steel" blocking the nozzle, and ensuring smooth continuous casting start-up.
     2. Improved Molten Steel Purity:
        1. Reduced Refractory Heat Absorption: The uniform high temperature of the lining minimizes the temperature drop of the molten steel, stabilizing the casting superheat, which is beneficial for the flotation of inclusions.
        2. Eliminating the Hazards of Moisture: Completely remove physical water and crystal water from the refractory material to prevent secondary oxidation and hydrogenation of molten steel.
     3. Adaptable to high-speed continuous casting: Shorter baking time perfectly matches the requirements of high-speed continuous casting machines for rapid turnover of intermediate vessels.
     4. Extend refractory life: Uniform heating reduces thermal stress, extending the service life of refractory materials such as intermediate vessel linings, slag barriers, and turbulence controllers.
3. Iron Ladle/Torpedo Car Baking and Insulation:
   • Application : Baking (after cold repair) and insulation (while waiting for iron addition or during transportation) of iron-containing containers during turnover.
   • Advantages Deepened:
     1. Energy saving and consumption reduction: Significantly reduces gas consumption during the baking/insulation process.
     2. Reduce molten iron temperature drop: High-temperature and uniform lining/tank lining reduces the temperature drop of molten iron during transportation and waiting (can reduce by 10-25℃), ensuring stable molten iron temperature entering the converter/electric furnace, reducing steelmaking energy consumption or increasing scrap ratio.
     3. Extend tank lining life: Uniform baking reduces thermal stress impact on refractory materials.
     4. Improve turnover rate: Fast baking/heating shortens the turnover time.
4. Molten Steel Tanker/Ladle Baking and Insulation:
   • Application: Baking and insulation of smaller containers for transporting molten steel within the steelmaking workshop (especially before or after refining while waiting for casting).
   • Advantages: Similar to steel ladle baking, focusing on insulation energy saving, reducing temperature drop, and stabilizing refining/casting temperature. Due to the smaller capacity, higher requirements for rapid heating are needed, and the advantages of oxygen-enriched/full-oxygen combustion are obvious.
5. Vacuum Refining Furnace Baking:
   • Application: Preheating baking of molten steel tanks (or lower troughs in the vacuum chamber) in vacuum refining equipment such as RH, VD, and VOD.
   • Advantages:
     1. Ensure refining effect: High-temperature tank lining reduces the temperature drop of molten steel in the initial stage of vacuum treatment, ensuring sufficient refining temperature and time window, which is crucial for degassing, decarbonization, and composition adjustment.
     2. Improve efficiency: Shorten baking time and speed up refining furnace turnover.
     3. Protect vacuum equipment: Thoroughly bake and remove moisture to prevent damage to the vacuum extraction system due to condensation of a large amount of water vapor.
6. Slag Pot/Slag Pan Baking (Specific Needs):
   • Application: Preheating of slag pots/pans used to hold high-temperature molten slag before use (the main purpose is to remove moisture and prevent violent splashing or even explosion of molten slag when it contacts a cold container).
   • Advantages:
     1. Inherent safety: Rapid and thorough removal of moisture is the key to preventing "explosion" accidents. The efficient drying capacity of oxygen-enriched/full-oxygen combustion is particularly important.
     2. Extend slag pot life: Preheating reduces thermal shock and prevents cracking of the slag pot due to rapid heating and cooling.
     3. Reduce slag adhesion: The higher surface temperature of the container after preheating can reduce molten slag adhesion and facilitate subsequent slag removal.

4.1.3、Summary of Application Benefits

4.1.4、Key Points for Application Implementation

1. Oxygen Source and Cost: A stable and economical oxygen supply (oxygen generator or liquid oxygen) is required. A detailed input-output analysis should be conducted to ensure that energy-saving benefits can cover the increased oxygen cost.
2. Burner and System Design: It is necessary to select or design special burners suitable for oxygen-enriched/full-oxygen combustion, optimize the combustion chamber and airflow organization, ensure stable and efficient combustion, reasonable flame shape, and avoid local overheating. Full-oxygen combustion needs to pay special attention to NOx control technology (such as staged combustion, flue gas recirculation FGR).
3. Refractory Adaptability: At extremely high temperatures, it is necessary to ensure that the refractory lining can withstand it, avoiding accelerated damage. Optimize the baking curve.
4. Intelligent Control System: Precise control of parameters such as oxygen concentration/flow rate, fuel flow rate, baking temperature curve, and furnace pressure is crucial for leveraging technological advantages and ensuring safe and stable operation.
5. Safety Measures: High-concentration oxygen environments place extremely high demands on equipment sealing, operational procedures, and safety interlocks. Relevant safety regulations must be strictly followed.

4.1.5 Development Trends

1. Deep Integration with Waste Heat Recovery: Utilize high-temperature flue gas to preheat combustion oxygen or coal gas, further improving system energy efficiency.
2. Intelligent and Big Data Applications: Intelligent baking models based on furnace conditions, refractory material status, and production plans to achieve adaptive optimal control.
3. Low-carbon/Zero-carbon Fuel Applications: Explore the combination of oxy-fuel/all-oxygen combustion technology with low-carbon/zero-carbon fuels such as hydrogen and biomass gas to help the steel industry achieve deep decarbonization.
4. Standardization and Modular Design: Reduce costs and facilitate promotion and maintenance.

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