The process flow of the air separation tower
1. Air compression and pre-cooling
The first step in the air separation tower process is to compress the atmospheric air. Through multiple stages of air compressors, the air is pressurized to a pressure of 5-7 bar. During the compression process, the temperature of the compressed air also rises, so intermediate coolers and post-coolers must be used to reduce the temperature of the air. To prevent the compressor from being damaged by impurities in the air, particles in the air are removed through filters. The compressed air is then sent to the pre-cooling system for further cooling, typically using cooling water or refrigerants such as Freon, to cool the air to approximately 5°C.
2. Air purification and dehydration
The pre-cooled air contains a small amount of moisture and carbon dioxide. These impurities may form ice at low temperatures and block equipment. Therefore, the air needs to be purified and dehydrated. This process is usually carried out using molecular sieve adsorption towers, through periodic adsorption and regeneration processes to remove water vapor, carbon dioxide, and hydrocarbons, etc., to ensure the smooth operation of the subsequent low-temperature processes. The purified air is clean and dry, suitable for subsequent cooling and separation processes.
3. Cooling of the main heat exchanger with air
The purified air is cooled to a depth through the main heat exchanger. The main heat exchanger is one of the most critical equipment in the air separation tower process. The air in the main heat exchanger undergoes heat exchange with the separated cold nitrogen and oxygen, causing its temperature to drop to close to the liquefaction temperature. The heat exchange efficiency during this process directly affects the energy consumption and product purity of the air separation tower. Typically, efficient aluminum plate fin heat exchangers are used to improve heat exchange efficiency.
4. Separation process in the distillation tower
The cooled air is sent to the distillation tower, where the separation of air components based on their boiling point differences is carried out. The air gradually liquefies at low temperatures, forming liquid air. This liquid air enters the distillation tower for multiple interactions between gas and liquid phases. In the distillation tower, oxygen, nitrogen, and rare gases such as argon are separated, with the oxygen concentration gradually increasing at the bottom of the tower and nitrogen being separated at the top. Through distillation, pure oxygen and nitrogen with higher purity can be obtained.
5. Extraction of oxygen and nitrogen products
The extraction of oxygen and nitrogen is the final step of the air separation tower process. Liquid oxygen and nitrogen are separated from the distillation tower and heated back to room temperature through heat exchangers to achieve the desired gaseous oxygen or nitrogen state. These gas products are further sent to storage tanks or directly supplied to users. To improve process efficiency and product purity, sometimes a dual-tower structure is designed to further separate argon from oxygen and nitrogen for industrial use.
6. Control and optimization
The entire air separation tower process involves a complex control system, requiring real-time monitoring and adjustment of compression, cooling, heat exchange, and separation processes to ensure the quality of the final products. Modern air separation towers are usually equipped with automated control systems, using sensors and control software to precisely regulate parameters such as temperature, pressure, and flow to optimize energy consumption and the purity of gas products in the production process.
The process flow of the air separation tower involves multiple steps such as air compression, pre-cooling, purification, deep cooling and distillation. Through these processes, oxygen, nitrogen and rare gases in the air can be effectively separated. The development of modern air separation tower technology has made the separation process more efficient and with lower energy consumption, which is of great significance for the application of industrial gases.
