Analysis of Application Scenarios for Nitrogen Generators in Steel Plants

In the steel-smelting process, nitrogen, as an inert gas, plays crucial roles such as isolating oxygen to prevent oxidation and aiding in cooling. As an efficient device for producing nitrogen, nitrogen generators have become indispensable key equipment in the production processes of steel plants. This article will provide a detailed introduction focusing on the core applications of nitrogen generators in steel plants, highlighting their significant contributions to enhancing steel quality, reducing energy consumption, and boosting overall efficiency in steel production.

I. Bottom and Top Blowing Protection in Converter Steelmaking

In the converter steelmaking process, the high-purity nitrogen produced by the nitrogen generator is primarily used for bottom-blowing and top-blowing protective operations. During converter steelmaking, gases need to be introduced into the furnace to achieve stirring of the molten steel, decarburization, and temperature elevation. However, if air is used, the oxygen content in the air would cause oxidation of the molten steel, leading to the formation of numerous oxide inclusions that compromise steel quality. In contrast, the nitrogen supplied by the generator boasts a purity level of 99.9% or higher. When injected into the bottom or upper part of the converter, it effectively isolates the molten steel from direct contact with ambient air, preventing oxidative reactions from occurring. Meanwhile, the stirring effect of nitrogen helps ensure uniform distribution of steel composition and stabilizes temperature profiles, facilitating the efficient removal of harmful gases such as carbon monoxide. As a result, the purity of the molten steel is significantly enhanced, while also boosting overall smelting efficiency and reducing the complexity of subsequent refining processes.

II. Mold Protection and Billet Shell Cooling During Continuous Casting

Continuous casting is the critical process that transforms molten steel continuously into steel billets. In this step, the demand for nitrogen is particularly crucial, and nitrogen generators play a dual and vital role. First, inside the crystallizer, molten steel comes into contact with the copper walls, where it cools and solidifies to form the billet shell. However, if air is present within the crystallizer, an iron oxide scale will form on the surface of the molten steel. This not only compromises the surface quality of the billet but can also lead to wear on the copper walls of the crystallizer. To prevent these issues, nitrogen generated by the nitrogen system is introduced into the crystallizer via a sealed device, creating an inert atmosphere that effectively inhibits oxidation on the steel surface, ensuring a smooth, flawless billet finish. Second, nitrogen can also serve as a cooling medium. It is delivered through pipelines directly to the crystallizer’s cooling system, where it helps maintain optimal temperatures for the copper walls. By carefully controlling the temperature gradient within the crystallizer, nitrogen ensures uniform growth of the billet shell, preventing defects such as uneven solidification or overheating—both of which could trigger dangerous "steel leakage" incidents. Ultimately, this reliable cooling mechanism safeguards the continuity and stability of the continuous casting process.

III. Atmosphere Control and Energy Conservation in Steel Billet Heating Furnaces

In the steel billet heating furnace process at the steel plant, nitrogen generated by the nitrogen generator is used for atmosphere control, helping to conserve energy, reduce consumption, and improve the quality of steel billets. When steel billets are heated in the furnace, excessive oxygen inside can lead to surface oxidation and burn-off, resulting in significant metal loss. Moreover, the resulting iron oxide scale may negatively impact the quality of products during subsequent rolling operations. By introducing nitrogen into the furnace, the nitrogen generator effectively dilutes the oxygen concentration, thereby minimizing oxidation and burn-off of the steel billets and reducing metal waste. Additionally, nitrogen's inert properties help maintain a stable heating atmosphere within the furnace, preventing localized temperature fluctuations—whether too high or too low—and ensuring uniform heating of the billets, thus enhancing overall heating quality. Meanwhile, precise nitrogen atmosphere control also optimizes the furnace's combustion efficiency, cutting fuel consumption and lowering both the enterprise's energy costs and carbon emissions. This approach aligns perfectly with the current green and low-carbon development goals of the steel industry.

4. Cooling and Rust-Proof Treatment After Steel Rolling

After steel rolling is completed, it requires cooling and rust-prevention treatment. In this process, the nitrogen gas produced by the nitrogen generator plays a crucial supporting role. The temperature of the rolled steel remains high at this stage; if allowed to cool directly in contact with air, its surface would readily react with oxygen and moisture, leading to rust formation and compromising both the steel's appearance and its corrosion-resistant properties. However, the nitrogen gas supplied by the generator can serve as an effective cooling medium, enabling rapid cooling of the steel through spraying or purging methods. At the same time, the nitrogen-rich atmosphere effectively isolates the steel from ambient air, preventing oxidation and rusting during the cooling process. Moreover, in the production of certain high-precision steel grades, nitrogen is also used to protect the steel’s surface after rolling, safeguarding it from environmental factors during subsequent handling and storage. This not only extends the steel’s shelf life but also ensures that the final product meets the stringent quality standards required by downstream industries.

V. Sealing and Safety Assurance for the Blast Furnace Gas Purification System

Blast furnace gas is an important secondary energy source in steel plants, and the sealing and safe operation of its purification system are absolutely critical. In this scenario, nitrogen generated by a nitrogen generator is used for sealing protection, ensuring the system remains secure. Blast furnace gas contains flammable and explosive gases such as carbon monoxide. During the purification process, if sealing devices—such as electrostatic oil traps or scrubbing towers—fail to maintain tight integrity, air can infiltrate the system, potentially forming an explosive gas mixture and leading to safety hazards. To prevent this, the nitrogen generator supplies nitrogen into the sealing areas of the purification system, creating a positive-pressure seal that effectively blocks outside air from entering equipment interiors. At the same time, nitrogen helps dilute any leaked gas concentrations within the system, significantly reducing the risk of explosions. Moreover, nitrogen is also utilized in purging operations of the purification system. Before maintenance work begins, nitrogen is introduced to completely displace the residual gas inside the system, ensuring the safety of maintenance personnel. After repairs are completed, nitrogen is again used to purge out any remaining air, preparing the system for a safe restart. This meticulous approach not only guarantees the stable and secure operation of the blast furnace gas purification system but also enables the efficient recovery and reuse of secondary energy resources.