Characteristics of growth and cool storage of CO2 hydrates produced in direct-contact way

With initial water at 26℃ and 15℃ and charge pressure at 3.6—4.2 MPa in the reaction kettle, the hydrates growth and cool storage characteristics of CO2 hydrates produced in direct-contact way were studied. When initial water was at 15℃ and charge pressure was at 3.6 MPa, precooling time was short, about 11min, and sub-cooled temperature was about 1.3℃ but temperature increment was not obvious at the beginning of growth, and total cool storage average rate and efficiency were about 82.4 kJ·min −1 and 4.34 respectively. At other temperatures and pressures, there were longer precooling time (between 20—55 min, but decreasing with the increase of charge pressure), higher sub-cooled temperature (at 5.5—9.7℃), rapid growth rate and dense hydrates. Temperature increment was obvious and the largest was at 4.0 MPa; hydrates average growth rate, total storage amount, total cool storage average rate and efficiency increased with the increase of charge pressure, and their maximum values at the experimental initial water temperatures were 77 and 154 g·min −1 , 3.725 and 3.791 MJ, 64.1 and 99.5 kJ·min −1 , 3.14 and 4.91 respectively. The hydrates decomposition releasing cool was a phase