Phase equilibrium measurements for clathrate hydrates of flue gas (CO2+N2+O2) in the presence of tetra-n-butyl ammonium bromide or tri-n-butylphosphine oxide

Abstract

Please cite this article as: J. Du, L. Wang, Phase equilibrium measurements for clathrate hydrates of flue gas (CO 2 + N 2 + O 2 ) in the presence of tetra-n-butyl ammonium bromide or tri-n-butylphosphine oxide, J. Chem. Thermodynamics (2015), doi: http://dx.doi.org/10. 1016/j.jct.2015.04.023 This is a PDF file of an unedited manuscript that has been accepted for publication. As a service to our customers we are providing this early version of the manuscript. The manuscript will undergo copyediting, typesetting, and review of the resulting proof before it is published in its final form. Please note that during the production process errors may be discovered which could affect the content, and all legal disclaimers that apply to the journal pertain. Abstract This paper reports the measured hydrate phase equilibria of simulated flue gas (12.6 vol% CO 2 , 80.5 vol% N 2 , 6.9 vol% O 2 ) in the presence of tetra-n-butyl ammonium bromide (TBAB) or tri-n-butylphosphine oxide (TBPO), at 0 wt%, 5 wt%, and 26 wt%, respectively. The measurements of the phase boundary between hydrate-liquid-vapor (H-L-V) phases and liquid-vapor (L-V) phases were performed within the temperature range (275.97 -293.99) K and pressure range (1.56 -18.78) MPa with using the isochoric step-heating pressure search method. It was found that addition of TBAB or TBPO allowed the incipient equilibrium hydrate formation conditions for the flue gas to become milder. Compared to TBAB, TBPO was largely more effective in reducing the phase equilibrium pressure.

Semiclathrate Hydrates in Tri-n-butylphosphine Oxide (TBPO)–Water and TBPO–Water–Methane Systems

“…It has been suggested 31 that several hydrates can be formed in the system, and TBPO•28H 2 O was previously reported as their averaged composition. Most recently reported data on P, T hydrate phase equilibria for aqueous solutions of TBPO + CH 4 , 32,33 + CO 2 , 32,33 + N 2 , 33 + H 2 , 32 + simulated biogas (60 mol % CH 4 + 40 mol % CO 2 ), 34 + simulated mine ventilation air (0.5 vol % CH 4 + 99.5 vol % air), 35 + simulated flue gas (12.5 vol % CO 2 + 80.5 vol % N 2 + 6.9 vol % O 2 ) 36 showed a shift of the hydrate phase equilibria to lower pressures and higher temperatures, compared to the corresponding gas + water system. These observations are evidence of the inclusion of gas molecules into the cavities of the TBPO hydrate structure.…”

Recent Advances in Experimental Measurements of Mixed-Gas Three-Phase Hydrate Equilibria for Gas Mixture Separation and Energy-Related Applications

“…They concluded that TBPO at 5 wt % exhibits a stronger promotion effect at all temperatures examined, while the case of 26 wt % TBPO performs better for temperatures above 287 K. Additional details for the conditions of the experimental measurements are reported in Tables S2a and b of the Supporting Information. Figure 4 also shows the experimental data of Du and Wang 96 for the ternary mixture, as well as the experimental data of Lee et al 59 and Sun et al 62 for the case of the binary mixture CO 2 + N 2 with a composition of 10 and 90 vol %, respectively (i.e., lumping the amounts of N 2 and O 2 ), which are the closest available binary mixtures to the ternary studied by Du and Wang. 96 Given the scarcity of the experimental data, especially for the ternary system, we recommend that additional measurements should be performed for the ternary case.…”

“…Figure 4 also shows the experimental data of Du and Wang 96 for the ternary mixture, as well as the experimental data of Lee et al 59 and Sun et al 62 for the case of the binary mixture CO 2 + N 2 with a composition of 10 and 90 vol %, respectively (i.e., lumping the amounts of N 2 and O 2 ), which are the closest available binary mixtures to the ternary studied by Du and Wang. 96 Given the scarcity of the experimental data, especially for the ternary system, we recommend that additional measurements should be performed for the ternary case. From the above discussion, it is evident that for the particular system (GM-2) there is plenty of room for future experimental and computational studies, especially if strong evidence becomes available for the need to perform delumping of N 2 and O 2 in the analysis.…”

“…Du and Wang 96 reported the only available (to the best of our knowledge) experimental study that examined the ternary flue gas mixture CO 2 + N 2 + O 2 with a composition of 12.6, 80.5, and 6.9 vol %, respectively. The authors reported threephase equilibrium measurements for the ternary gas mixture, as well as for the case of semiclathrates with the presence of TBAB or TBPO at 5 and 26 wt %.…”