https://doi.org/10.3389/fenrg.2021.785039
“According to Dong et al. (2010), CO2 solubility has been measured in the stainless-steel reactor. The apparatus contains four 400 cm3 stainless-steel equilibrium cells (they have an identical structure with the one shown in Dong’s research) that were designed to operate at a temperature as high as 130°C and a pressure as high as 1 MPa, a 500 cm3 stainless-steel gas container with a temperature transducer and a pressure transducer on the top, and CO2 and N2N2 tanks.
The key part of the device is the gas–liquid balance reactor, and the temperature in the gas and liquid phases was controlled using a heating jacket and then determined by two temperature transducers, whose accuracy was 0.1 K. A stirring paddle equipped in the kettle is driven by the external motor to generate magnetic force and drive the solution inside of the sealed kettle. The overall pressure was determined by a pressure transducer (JYB-KO-HAA, Kunlunhaian Co.), whose accuracy was about 0.5%. Meanwhile, the same temperature and pressure transducers were adopted by the CO2 gas container, which is used to obtain the total amount of CO2 that was introduced into the reactor by recording the pressure difference before and after each injection. Due to the simple structure of the gas chamber, the actual volume can be directly calibrated by the drainage method. However, the internal structure of the reactor is complicated and cannot be directly measured by the drainage method. Its actual volume is calibrated by the gas pressure difference method after measuring the volume of the CO2 gas chamber. At the beginning of each experiment, the reactor cell is washed by the remaining air through N2, and then, the aqueous amine solution with a volume of 100 cm3 is injected into the cell. Meanwhile, the temperature of the reactor was set at the experiment temperature. Later, CO2 was injected to the cell, and 10 h was provided for the absorption equilibrium after every injection.
The partial pressure of CO2 was obtained by determining the increase in the total pressure compared to the initial value after an injection of CO2, and it was assumed that the partial pressure of N2 and H2O was constant in each experiment. Using the Peng–Robinson (PR) cubic equation, the exact quantity at the gas phase was judged by three factors, including volume, pressure, and temperature (Peng and Robinson, 1976). Then, the dissolved CO2 concentration was expressed by CO2 loading with mole CO2/mole amine. The loading uncertainty was 8%, which was determined by the uncertainty of pressure, temperature, and volume, which were 0.5%, 0.1, and 0.5%, respectively. The uncertainty of CO2 partial pressure was estimated as 2%, and the details are shown in the study by Dong et al. (2010).”