Modern cryogenic air separation equipment must be equipped with molecular sieve purification system, which is the core premise to ensure long-term safe and stable operation of equipment. The combination of alkali washing and drying tower was used for the old plant in the early stage, but the purification accuracy was low and the energy consumption was high, which had been replaced by molecular sieve. The cryogenic air separation without molecular sieve was only applicable to very small test units or temporary working conditions, and long-term production could not be realized.
The core function of molecular sieve is to deeply remove water, carbon dioxide and hydrocarbon impurities in the air under normal temperature. The residual water after precooling will freeze when entering the - 170 ℃ - - 190 ℃ cold box, and the carbon dioxide will solidify into dry ice, which will block the heat exchanger and rectification tower, resulting in equipment shutdown; Molecular sieve can remove water to dew point ≤ - 70 ℃ and carbon dioxide to ≤ 1ppm to completely avoid blocking.
More importantly, molecular sieve can eliminate the explosion risk. Trace amount of acetylene and other hydrocarbons in the air are easy to be concentrated in liquid oxygen, which is very easy to cause accidents after reaching the explosion limit. The molecular sieve can remove acetylene to ≤ 0.01ppm, and build a solid security line.
In addition, the molecular sieve has high adsorption efficiency and strong selectivity. With the double-column alternate working mode, it can realize uninterrupted gas supply. In addition, the energy consumption is far lower than the traditional method by using the polluted nitrogen for regeneration, and its function cannot be replaced by silica gel, activated alumina and other materials. It is an indispensable key component of the cryogenic air separation equipment.
