Zeolite molecular sieves play a vital role in the pre-purification stage of cryogenic air separation industry. Before air enters the main air separation unit, it flows through a molecular sieve bed to eliminate impurities that could disrupt cryogenic operations or compromise final product quality.
Overview Of Cryogenic Air Separation Technology
Cryogenic air separation technology leverages the boiling point differences of various gaseous components in air. It first chills air to ultra-low temperatures below -180°C, colder than the boiling point of every gas component in air, then separates individual gases through distillation based on their boiling point disparities.
This technology serves as a core industrial gas separation method with extensive applications across steel, chemical, electronics, medical, and aerospace sectors. It remains the most mature and efficient approach for industrial production of oxygen, nitrogen, argon, and other rare gases.
Cryogenic Distillation Air Separation Process
The cryogenic distillation air separation process consists of six core operational steps:
- Air Compression
Multi-stage compressors pressurize air to create the required pressure conditions for air cooling and subsequent gas separation. Conventional pressure ranges sit between 0.5 MPa and 0.8 MPa for standard-pressure units, while high-pressure units operate at 3 MPa to 6 MPa.
- Pre-cooling
Coolers that use cooling water or refrigerant media lower air temperature to the liquefaction threshold of approximately 5°C to 10°C. This step cuts down energy consumption for the subsequent cryogenic separation process.
- Pre-purification
Adsorption towers filled with molecular sieves, activated alumina, and other adsorbent materials remove moisture, carbon dioxide, hydrocarbons, and other impurities from air. This prevents equipment freezing and blockage at low temperatures and ensures stable and safe cryogenic process operation.
- Deep Cooling
Purified air conducts heat exchange with cold air streams and gradually cools to the liquefaction temperature of -170°C to -180°C, turning part of the gaseous components in air into liquid state.
- Distillation Separation
The high-pressure column separates air into oxygen-rich liquid and nitrogen-rich liquid. Further distillation in the low-pressure column produces high-purity oxygen and nitrogen products, while the system extracts argon gas from the middle section of the low-pressure column.
- Gas Extraction And Storage
The system reheats separated oxygen, nitrogen, and argon back to gaseous state for direct output. It also liquefies partial gas products such as liquid oxygen and liquid nitrogen for storage. Custom high-purity products are available, including oxygen with purity above 99.5%, nitrogen above 99.9%, and argon above 99.9%.
Molecular Sieves For Cryogenic Air Separation
Different types of 13X series zeolite molecular sieves deliver targeted adsorption and separation performance for cryogenic air separation scenarios:
- 13X-APG Molecular Sieve
Custom-developed for the cryogenic air separation industry, 13X-APG adapts to air cryo-separation devices of all scales and features strong selective adsorption capacity for water and carbon dioxide.
- 13X-HP Molecular Sieve
13X-HP excels in oxygen-nitrogen separation and maintains a stable oxygen production rate. It mainly supports oxygen generation units to separate oxygen and nitrogen and produce enriched oxygen for industrial and medical use.
- 13X-APG-III Molecular Sieve
As an upgraded version of the standard 13X-APG sieve, it boasts 60% to 70% higher overall adsorption performance. 13X-APG-III retains excellent adsorption capacity even in environments with low carbon dioxide concentrations.
- 13X-APG-V Molecular Sieve
This high-end model delivers more than twice the adsorption performance of conventional 13X-APG and over 1.4 times that of 13X-APG-III. 13X-APG-V stands as a leading high-performance material in the cryogenic air separation industry, with comprehensive performance indicators far exceeding earlier generation products.
