Recycling Devices for Supercritical Carbon Dioxide

Except for analytical and small preparative instruments, CO2 recychng after solute separation is common practice. If this were not the case, CO2 consumption would easily exceed 10 or even 20kg of liquefied gas per hour for a preparative SFC system equipped with a 50-nim id column. Gas leaving the separators should be brought back into the same physical state and be at the same pressure as a fresh fluid delivered from the supply unit. Since liquid pumps are most often used in SFC equipment, gaseous eluent must be liquefied prior to recycling. 

The preferred solution is CO2 recycling at a pressure of about 40-50 bar, slightly below the typical pressure inside CO2 cylinders stored at ambient temperature. Eluent recycling and condensation at this pressure requires cooling uhlities for a temperature range of 0-5 °C. Under these condihons the solute-eluent separation 

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