The lower tower of the air separation equipment is used to carry out primary rectification of air to obtain high-purity nitrogen and liquid air.
Development history, circulation (the development of overflow bucket includes straight bucket, inclined bucket and cross bucket), convection (single overflow, double overflow and four overflow), and packed tower. Development status, circulation or convection structure are used for small and medium-sized air separation. The large air separation unit adopts convection, four overflow (the overflow intensity of double overflow is too large), and the outlet overflow weir includes straight weir, curved weir, triangular weir and toothed weir; Packing tower is generally used for oversized air separation above 60000 grade, and sieve plate tower is not recommended.
The technical difficulties are as follows: A. mass transfer efficiency; b. Flatness of tray; c. Rigidity of overflow bucket. For sieve plate tower, the liquid layer is high, the process is long, and the liquid purity is high, but the resistance is large, and the gas penetration is small. At the same time, how to improve the distillation efficiency of the packed tower at about 5barG, as well as the layout and investment problems brought by the tower height, has also become a hot issue discussed by the industry in recent years.
The process organization of DEAR air separation plant has been diversified, and a lot of experience has been accumulated in terms of safety, reliability and stability. Technical difficulties have been overcome, and the optimization of the comprehensive investment of primary investment and operation consumption of the process has been reasonably selected according to the needs of users.
