Analysis of an activated-carbon sorption compressor operating with gas mixtures

Sorption compressors elevate the pressure of gases and can provide a more or less continuous mass flow. Unlike mechanical compressors, sorption compressors have no moving parts, and therefore do not emit vibrations and are highly reliable. There exist different sorption compressors for different operating conditions and various gases. However, there are no published reports of sorption compressors for mixed gases. Such compressors, among other applications, may drive mixed-refrigerant Joule–Thomson cryocoolers. The adsorption of mixed gases is usually investigated under steady conditions, mainly for storage and separation processes. However, the sorption process in a compressor goes through varying states and mass changes; therefore, it differs from the common mixed gases adsorption applications. In this research a numerical analysis for mixed gas sorption compressors is developed, based on pure gas adsorption characteristics and the ideal adsorbed solution theory. Two pure gas adsorption models are used for calculating the conditions of the adsorbed phase: Langmuir and Sips; and the Peng–Robinson equation of state is used to calculate the conditions of the vapor phase. Two mixtures are investigated; nitrogen–methane and nitrogen–ethane. Finally, the analysis is verified against experimental results. This research provides initiatory observation for mixed gases sorption compressor in which each component is differently adsorbed.