Production of Liquid Oxygen and Nitrogen Using Adsorptive Air-Fractionating Plant and Cryogenic Gas Machine

Abstract

A method of producing liquid oxygen and nitrogen employing an adsorptive air-fractionating plant and a cryogenic gas machine is described. The method is of practical interest for producing less than 15 kg/h of liquid oxygen and nitrogen.Methods of producing liquid nitrogen in small quantities (50-60 kg/h) employing Azh-0.05 type of air-fractionating plant that includes a cryogenic gas machine (CGM) and a fractionating column are well known [1]. The possibility of using CGM for liquefaction of natural gas has also been discussed [2].A variant of liquid nitrogen production employing an adsorptive air-fractionating plant for getting gaseous nitrogen (AAFP-N) and a Phillips CGM was described earlier [3] (Fig. 1).In this process flow diagram, the cold for cooling and liquefaction of gaseous nitrogen stream is supplied at a low temperature level T c(l) . In this case, the specific quantity of cold supplied for 1 kg of liquid is about 400 kJ/kg. In [4], the ratio of the real refrigerating machine performance coefficient ε r to the Carnot cycle refrigeration coefficient ε Car is given as a function of minimum temperature on the Phillips CGM head (single-stage helium machine).According to [5], this function can be approximated in the temperature range 70 K < T c < 120 K by the equation