Abstract
Amine scrubbing is the most important technique for capturing CO2. The cyclic diamine N-(2-Hydroxyethyl)-piperazine (HEPZ), a derivative of piperazine, with good mutual solubility in aqueous solution, a low melting point, and a high boiling point, has the potential to replace PZ as an activator added in the mixed amine system to capture CO2. In this study, the solubility of CO2 in aqueous HEPZ solutions was determined for three HEPZ concentrations and four temperatures. The VLE data for HEPZ-H2O were obtained using a gas–liquid double circulation kettle at pressure 30–100 kPa, and the thermodynamic model for the HEPZ-H2O-CO2 system was built in Aspen Plus based on the electrolytic non-random two-liquid (ENRTL) activity model. The physical parameters for HEPZ and the interaction parameters for ENRTL, along with reaction constants of carbamate reactions, were regressed. Using the thermodynamic model, the CO2 cyclic capacity, speciation with loading, and heat of reaction for the CO2 capture system by the aqueous HEPZ solution are predicted and analyzed.
Highlights
Power generation by burning fossil fuels is the most important source of greenhouse gas emissions that cause global climate change (Anderson, 2016)
This study studied the HEPZ aqueous solution for CO2 capture, aiming to develop a rigorous thermodynamic model of HEPZ/CO2/H2O to accurately calculate the energy consumption during the capturing and represent all relevant thermodynamic properties, such as vapor–liquid equilibrium (VLE), chemical reaction equilibrium, and heat capacity, which are important elements for the process simulation as well as optimization of CO2 capture
The heat capacity data of HEPZ obtained from the study by Poozesh et al (2013), Tagiuri (2019) were regressed to acquire the ideal gas heat capacity constants (Cipg), and Antoine’s constants were from the database of Aspen; the value and standard deviation are listed in
Summary
Power generation by burning fossil fuels is the most important source of greenhouse gas emissions that cause global climate change (Anderson, 2016). Good-performance absorbents can greatly reduce the operating cost of the capture process and generally need to have the following properties (Liang et al, 2015): the cyclic capacity is high, the reaction kinetics is fast, the heat of absorption is relatively low, the resistance to oxidative and thermal. Since no literature studied the absorption performance of the HEPZ aqueous solution and mixed-amine system with HEPZ, there is a need to measure the relevant experimental data. This study studied the HEPZ aqueous solution for CO2 capture, aiming to develop a rigorous thermodynamic model of HEPZ/CO2/H2O to accurately calculate the energy consumption during the capturing and represent all relevant thermodynamic properties, such as vapor–liquid equilibrium (VLE), chemical reaction equilibrium, and heat capacity, which are important elements for the process simulation as well as optimization of CO2 capture.
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