The air separation unit realizes the ultra-low temperature required for air liquefaction. The core is based on the principle of low-temperature refrigeration cycle and gas expansion and heat absorption. The whole system gradually reduces the normal temperature air to minus 196 ℃ liquefaction temperature by combining mechanical refrigeration, heat exchange cooling and throttling refrigeration, providing a low-temperature basis for air rectification and separation. Low temperature air separation is not a single equipment refrigeration, but a comprehensive refrigeration system with multi-stage cooling, step-by-step cold storage and cold energy recovery.
The core refrigeration equipment of air separation is a turbo expander, which is the core device for producing ultra-low cooling capacity. Part of the high-pressure clean air compressed by the air compressor, cooled by the precooling unit and purified by molecular sieve enters the expander for high-speed expansion to do work. The gas pressure is rapidly reduced and the internal energy is sharply reduced, achieving severe adiabatic cooling and generating most of the cooling capacity required for equipment operation. At the same time, it is equipped with air throttle valve for auxiliary refrigeration. The high-pressure air is throttled and depressurized to further reduce the medium temperature and make up for the cooling consumption of the system.
The cooling capacity of the equipment is recycled through the main heat exchanger, and the low-temperature reflux dirty nitrogen and product gas precooling the incoming normal temperature air, greatly reducing the cooling capacity loss and continuously accumulating the low-temperature working conditions. In the production process, the expander continues to make up cooling, the heat exchanger maintains high-efficiency cooling, and the cooling capacity is recovered in a closed loop. The three are coordinated and balanced to maintain the ultra-low and low temperature environment in the air separation tower and ensure the continuous and stable operation of air liquefaction and distillation purification.
