Characteristics of CO2-ionic liquids/PEG200 as new working pairs for absorption-compression refrigeration system

Abstract

Absorption-compression refrigeration system using CO2-Ionic Liquids (ILs) as working pairs could avoid the high operating pressure in transcritical CO2 refrigeration cycle. This work proposed using PEG200 as the additive to improve the physical properties of the pure ILs, making the absorption-compression refrigeration system being more efficient and less corroded. The effects of PEG200 on the CO2-ILs absorption and desorption, the viscosity and the corrosion behavior on stainless steel were investigated experimentally. Results show that PEG200 has positive effect on these key parameters at temperature of 293.15 K to 343.15 K and pressures up to 10.0 MPa. The addition of PEG200 to [emim][FAP] could increase the CO2 solubility by 10.17% maximally, reduce the viscosity by 24.43% maximally, and accelerate the desorption rate. The CO2 solubility increases with the pressure increasing, and decreases with the temperature increasing. The viscosity of the mixed solvent decrease with the increase of the temperature and pressure. The addition of PEG200 to [emim][Tf2N] effectively weakens the corrosion on the 316L stainless steel, the corrosivity of ILs/PEG200 is less than that of the pure ILs. This work shows ILs with PEG200 added have better physical properties as the CO2 absorbent, providing a new approach of selection for CO2 absorption.