Investigation of the kinetics of TBAB + carbon dioxide semiclathrate hydrate in presence of tween 80 as a cold storage material

Abstract

Because of large cold storage capacity and suitable freezing temperature of hydrate slurries, these materials could be used as a medium to store the cold energy in air conditioning systems. Semiclathrate hydrates of tetra n-butylammonium bromide (TBAB) are favorable phase change materials (PCMs), due to their moderate hydrate formation conditions. The kinetics of carbon dioxide - TBAB semiclathrate hydrate formation in presence and absence of tween 80 as a non-anionic surfactant is investigated in this research. The experiments were performed in a 169 cm3 stirred batch reactor at initial pressure of 3.2 MPa and isothermal condition of 276.15 K. Aqueous solutions of TBAB with concentrations of 0–15 wt% in presence and absence of tween 80 with concentrations of 500 and 1500 ppm are tested. The results revealed that utilization of TBAB with concentrations of 5–15 wt%, inhibits the kinetics of formed hydrates. By increasing the concentration of TBAB the amount and rate of gas uptake and storage capacity (SC) of formed hydrates decreases. Tween 80 with a concentration of 500 ppm presented a slight positive effect on the kinetics of hydrate formation in presence and absence of TBAB. While 1500 ppm of this additive inhibited the kinetics of formed hydrates.