Air separation and liquefaction: recent developments and prospects for the beginning of the new millennium

Earlier advances in air separation and liquefaction include improvements in: overall product recovery, feed air purification, more efficient heat exchange, optimum plant control, gradual improvement in efficiency of compressors and expanders. More recent improvements include use of structured packing in distillation columns, molecular sieve adsorbents for air purification, computer simulation and control of plants, and increased machinery efficiency. Advances in fabrication and construction techniques are aimed at reducing capital costs. This paper reviews modern developments in air separation and liquefaction and attempts in this context to suggest features that might be expected to arise in the early part of the third millennium.