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Aluminum Refineries

Brief History

Application of Chlorine in Aluminum Refineries

The history of aluminum refining can be traced back to the early 19th century when the process of extracting aluminum from its ore, known as alumina (aluminum oxide), was developed (Geller, 2007). The commercial production of aluminum began in the late 19th century, revolutionizing various industries due to its lightweight, high strength, and excellent conductivity properties.

In the early stages of aluminum refining, the Bayer process was primarily used, which involves the extraction of alumina from bauxite ore through a series of chemical reactions (Harbor Aluminum, n.d.). However, the production of high-quality aluminum required further refining to remove impurities and enhance its properties.

The introduction of chlorine gas offered several advantages, including its ability to react with impurities and form volatile chlorides that could be separated from molten aluminum. By reacting with these impurities, chlorine gas facilitated the formation of volatile chlorides, which had lower boiling points than aluminum. This enabled their separation from the molten aluminum, resulting in a refined and higher-quality aluminum product. The implementation of chlorine gas in the purification process significantly contributed to the development of aluminum refining techniques and the production of aluminum with improved structural integrity and purity.

The strategic implementation of chlorine gas in aluminum refineries revolutionized the industry by enabling the production of high-quality aluminum with enhanced properties. The use of chlorine gas for purification, fluxing, and equipment cleaning remains an integral part of modern aluminum refining processes, contributing to the production of superior aluminum products.

Today, aluminum refineries continue to utilize chlorine gas and advanced technologies to refine aluminum efficiently, meeting the stringent quality standards demanded by various industries, including automotive, aerospace, construction, and packaging.

Role of Chlorine in the Refining Process

Aluminum refineries rely on the strategic utilization of chlorine gas to achieve high-quality aluminum production. Chlorine gas is used in a number of stages in aluminum refining, rendering it a very important agent in the procedure itself. Aluminum refining involves three processes: fluxing, floatation, and filtration. Fluxing is performed in a pre-treatment crucible or casting furnace and removes alkali impurities using reactive salt or gas. The Alcan’s Treatment of Aluminum in Crucible (TAC) process, using a specially designed rotor and aluminum fluoride

salt, is commonly used for purification (Bell et al., 2003). Chlorine gas is crucial for fluxing, reacting with alkali metals and magnesium to form volatile chlorides that separate from the melt. Floatation and degassing processes further reduce impurities and hydrogen levels using chlorine gas mixed with nitrogen or argon. Filtration, using ceramic foam or deep-bed filters, removes small impurities before casting.

In the TAC process, chlorine gas plays a vital role in fluxing aluminum melts to remove alkali impurities. By reacting with alkali metals and forming volatile chlorides, chlorine gas enables the separation of impurities from the melt. The TAC process, using aluminum fluoride salt and a specially designed rotor, improves the efficiency of impurity removal. However, additional fluxing with chlorine gas is essential to meet commercial standards and achieve high purity in the aluminum product.

Chlorine gas is of great importance in the Rotary Gas Injection (RGI) process for fluxing aluminum melts. RGI uses a fraction of the chlorine gas compared to other methods, reducing emissions and the need for alkaline scrubbers. By injecting chlorine gas below the melt surface and dispersing it throughout the crucible, RGI effectively removes alkali impurities.

Additionally, chlorine gas helps reduce the concentration of hydrogen and oxides in the melt by causing these impurities to float to the surface. RGI is a widely used process in aluminum cast houses due to its effectiveness in increasing metal purity and minimizing chlorine emissions.

Chlorine gas plays a critical role in the degassing process of aluminum refining. Degassing aims to reduce hydrogen levels in the melt through floatation and is typically performed using chlorine gas mixed with nitrogen or argon. Chlorine gas is crucial for achieving low hydrogen levels and initiating alkali metal removal. The degassing process faces challenges such as chlorine gas dependence and metal retention in the vessel between castings or alloy changes. However, the development of the Alcan compact degasser (ACD) addresses metal retention issues by performing the process in an enclosed system. Chlorine gas remains irreplaceable in degassing practices, but its use in aluminum-magnesium alloys can form magnesium chloride impurities, which require careful monitoring and control.

Optimization of the Refining Process

The strategic implementation of chlorine gas in aluminum refineries offers significant benefits in terms of optimizing the refining process. By utilizing chlorine gas for purification, fluxing, and equipment cleaning, refineries can achieve improved efficiency and productivity while enhancing the quality and purity of the aluminum product.

The removal of impurities is a critical aspect of the refining process. Impurities such as magnesium, silicon, and other metals can negatively impact the properties and performance of aluminum (Davis et al., 2006). Chlorine gas plays a vital role in the purification of aluminum by reacting with these impurities and forming volatile chlorides. Through the process of distillation, these chlorides can be separated from the molten aluminum, resulting in a refined and high- purity aluminum product (Wu et al.). By effectively removing impurities, chlorine gas helps optimize the quality and purity of the final aluminum product, meeting the stringent standards and requirements of various industries.

Fluxing is another important application of chlorine gas in aluminum refining. By acting as a fluxing agent, chlorine gas facilitates the removal of oxides from the surface of the molten aluminum. These oxides, if not properly removed, can introduce impurities and compromise the structural integrity of the aluminum. The use of chlorine gas in fluxing enables the reduction or elimination of oxides, enhancing the overall structural integrity and performance of the aluminum product. This optimization of the refining process ensures that the aluminum meets the required specifications and can be utilized in various applications with confidence. Recent practices, however, have shifted from the injection of chlorine gas for fluxing (Tremblay et al., 2023) However, the role of chlorine gas in degassing procedures remains indispensable.

Introduction to Hydro Instruments:

In the field of aluminum refining, the selection of reliable and high-quality chlorine equipment is of utmost importance. Hydro Instruments emerges as a leading provider, offering a comprehensive product range specifically designed to meet the unique requirements of aluminum refining processes. With their expertise and dedication to excellence, Hydro Instruments has established a strong reputation as a trusted supplier in the industry.

Hydro Instruments’ product range encompasses a wide array of chlorine gas feed equipment tailored to address the specific needs of aluminum refineries. Among their offerings, gas feed systems and monitoring/control equipment stand out as essential tools in ensuring accurate and safe chlorine gas introduction, precise dosage control, and maintaining a secure working environment.

Gas Feed Systems:

Gas feed systems play a crucial role in the aluminum refining process by enabling the accurate and controlled introduction of chlorine gas. Hydro Instruments’ gas feed systems are designed with precision and reliability in mind. Equipped with advanced features such as flow meters, pressure regulators, and automatic shut-off valves, these systems ensure precise and consistent chlorine dosage. The accurate and safe delivery of chlorine gas is essential for optimizing the refining process and achieving the desired results in terms of impurity removal and equipment cleaning. Hydro Instruments’ gas feed systems provide the necessary control and reliability to meet these critical requirements.

Monitoring and Control Equipment:

Maintaining optimal chlorine levels in the aluminum refining process is vital for effective process optimization. Hydro Instruments recognizes the importance of monitoring and control equipment in achieving this goal.

Chlorine gas detectors are an integral part of maintaining a safe working environment. These devices continuously monitor chlorine gas concentrations in the air surrounding the storage and handling areas. Hydro Instruments’ chlorine gas detectors are equipped with advanced sensing technologies, providing reliable and early detection of any gas leaks or deviations from safe levels. This enables prompt action to mitigate potential hazards, ensuring the safety of refinery staff and maintaining a secure environment for the aluminum refining process.

By offering a comprehensive range of gas feed and monitoring equipment Hydro Instruments equips aluminum refineries with the necessary tools for accurate and controlled chlorine gas application, monitoring, and safety. The incorporation of Hydro Instruments’ equipment ensures efficient and effective chlorine disinfection while prioritizing the well-being of personnel and the integrity of the refining process.

Chlorine Dosage and Equipment Selection

Chlorine dosage and equipment selection play a vital role in achieving effective and efficient chlorine gas application in aluminum refineries. Proper monitoring of chlorine levels and selecting the appropriate equipment are essential to ensure safe and optimal refining processes.

When determining the appropriate chlorine dosage, several factors must be taken into consideration. Refinery size, temperature, and the specific requirements of the aluminum refining process all influence the amount of chlorine gas required. Larger refineries may necessitate higher chlorine dosages to achieve the desired purification and cleaning efficacy. Temperature is another crucial factor to consider, as it affects the rate of chlorine decay and the chlorine demand of the aluminum refining process. Higher temperatures generally require higher chlorine dosages due to increased chlorine decay rates.

Hydro Instruments, as a leading provider of chlorine gas feed equipment, offers guidance for chlorine dosage and equipment selection in aluminum refineries. Our expertise and knowledge in the field help refineries determine the optimal chlorine dosage based on these factors.

The appropriate selection of equipment is equally important for accurate chlorine gas application. Hydro Instruments offers a range of gas feed systems suitable for various refinery sizes and requirements. Refineries can select the equipment that best matches their needs, taking into account factors such as gas flow rate, control options, and safety features. Hydro Instruments products are designed with precision and reliability in mind, ensuring precise and consistent chlorine dosage while maintaining the safety of the refining process.

Conclusion

In conclusion, chlorine gas plays a crucial role in aluminum refining processes by enabling purification, acting as a fluxing agent, and facilitating equipment cleaning. Its applications enhance the quality and purity of aluminum while optimizing the refining process. Hydro Instruments’ chlorine gas feed and control equipment offers reliable solutions for aluminum refineries, ensuring effective and safe chlorine gas utilization. By understanding and implementing these applications, aluminum refineries can achieve superior aluminum production while maintaining a safe and hygienic environment.

Bibliography

  1. Geller, T. (2007, December 3). Aluminum: Common metal, uncommon past. Aluminum: Common Metal, Uncommon Past. https://sciencehistory.org/stories/magazine/aluminumcommon-metal-uncommon-past/
  2. Aluminum production & manufacturing process explained. HARBOR Aluminum. (n.d.). https://www.harboraluminum.com/en/aluminum-process
  3. Bell, S., Davis, B. R., Javaid, A., & Essadiqi, E. (2003). Final Report on Refining Technologies of Aluminum. https://doi.org/10.13140/RG.2.2.27655.39847
  4. Davis, B. R., Javaid, A., & Essadiqi, E. (2006). Final Report on Effect of Impurities in Aluminum. ResearchGate. https://doi.org/ 10.13140/RG.2.2.34366.28482
  5. Wu, J., Djavanroodi, F., Gode, C., Attarilar, S., & Ebrahimi, M. (2022). Melt refining and purification processes in al alloys: A comprehensive study. Materials Research Express, 9(3), 032001. https://doi.org/10.1088/2053-1591/ac5b03
  6. Tremblay, S.; Desrosiers, L.; Levesque, D. Use of a Tertiary Salt Flux of NaCl, KCl, and MgCl2 for the Purification of Aluminium or Aluminium Alloys, and Method Thereof.

U.S. Patent US 2012/0017726, 26 January 2012