1,720,986 research outputs found
Recovery of CO2 from flue gas using gas hydrate: Thermodynamic verification through phase equilibrium measurements
No full textThe main purpose of this study was to develop a new hydrate-based gas separation (HBGS) process especially for recovering CO2 from flue gas. Temperature and pressure conditions for hydrate formation have been closely examined at the various CO2 concentrations of flue gases. Tetrahydrofuran (THF) chosen as a hydrate promoter can also participate in forming hydrates and produces a mixed hydrate together with CO2. The hydrate stability region was greatly expanded by using THF for lowering the equilibrium formation pressure. To confirm thermodynamic validity of the HBGS process, the three-phase equilibria of hydrate, liquid, and vapor we re measured for the systems comprising CO2, Ng and water with or without THF in the temperature range of 272-295 K. In addition, two phase equilibria of hydrate and vapor were experimentally investigated for the same systems at several temperatures. Through close examination of the overall experimental results, it was firmly verified that the HBGS process makes it possible to recover more than 99 mol % of CO2 from the flue gas. The key unit operations of the HBGS lie in hydrate formation and subsequent dissociation similarly to gas absorption and desorption using the sterically hindered amines. The HBGS provides several advantages over the conventional ones. First, the operational temperature is moderate in the range of 273-283 K, and continuous operation allows this process to treat a large amount of gaseous stream. Second, only a small amount of THF is needed together with water and therefore severe corrosion problem can be avoided. Third,the aqueous solution containing THF after dissociation can be easily recycled to the hydrator.This work was supported by the Brain Korea 21 Project and grant No. 98-0502-04-01-3 from the Basic Research program of the KOSEF
Clathrate phase equilibria for the water-phenol-methane system
No full textClathrate phase equilibria for the ternary water-phenol-methane system were studied. This system consisted of two hosts and one guest. Four-phase equilibrium boundary for this ternary system was measured over the temperature and pressure ranges of 283.2 K and 37.0 bar to 323.6 K and 275.0 bar. Isobaric equilibrium compositions were also measured at 50.0 bar and several temperature ranges. Several types of three-phase and four-phase diagrams were obtained, which were dependent on the feed concentration of methane. Separation of phenol from aqueous solution was depicted in a diagram on the basis of methane-free concentration. A schematic pressure-temperature diagram for the ternary and three corresponding binary systems was presented. (C) 1998 Elsevier Science B.V. All rights reserved
Equilibrium dissociation pressures for p-cresol plus methane and p-cresol plus nitrogen clathrates at temperatures above the normal melting temperature of p-cresol
No full textClathrate phase equilibria for the two binary p-cresol + methane and p-cresol + nitrogen systems were measured above the normal melting temperature, 307.6 K, of p-cresol. Three-phase (clathrate + liquid + vapor) dissociation pressures ranged from 79.7 bar to 300.0 bar for the p-cresol + methane system and 99.9 bar to 338.8 bar for the p-cresol + nitrogen system. In additon, the three-phase (solid + liquid + vapor) equilibrium data of the p-cresol + nitrogen system are presented for comparison
Experimental Measurement of Clathrate Phase Equilibria containing Carbon Dioxide, Methane, Phenol and p-Cresol
No full textEnthalpies of dissociation of clathrate hydrates of carbon dioxide, nitrogen, (carbon dioxide plus nitrogen), and (carbon dioxide plus nitrogen plus tetrahydrofuran)
No full textA calorimetric technique is described for measuring the enthalpy of dissociation liberated from solid hydrates. In this study, the enthalpies of dissociation were determined at T = 273.65 K and p = 0.1 MPa for simple and mixed hydrates of carbon dioxide, nitrogen, (carbon dioxide + nitrogen), and (carbon dioxide + nitrogen + tetrahydrofuran) using an isothermal microcalorimeter. The addition of tetrahydrofuran (THF) promoted hydrate stability and increased the number of guest molecules encaged in the small and large cavities of the hydrate lattice, resulting in lower enthalpy of dissociation, compared with structure It hydrate. The composition ratio of guest molecules did not affect the enthalpy of dissociation, which was found to be nearly constant for the same mixture. (C) 2001 Academic Press.This work was supported by grant No. 98-0502-04-01-3 from the Basic Research program
of the KOSEF and also partially by the Brain Korea 21 Project
Clathrate phase behavior of the phenol-methane, phenol-carbon dioxide and phenol-nitrogen systems
No full textThree-phase, solid clathrate-phenol-rich liquid-vapor, equilibrium lines for the two binary phenol-methane and phenol-carbon dioxide systems were measured using a newly-designed equilibrium apparatus. The measured clathrate dissociation pressure and corresponding temperature ranges are 88.8-326.8 bar and 312.4-325.4 K for the phenol-methane system and 21.0-99.2 bar and 314.2-319.3 K for the phenol-carbon dioxide system. An abrupt increase of dissociation pressures appeared near 319 K for the phenol-carbon dioxide system, while the phenol-methane system shows a continuous increase of dissociation pressures with no abrupt change over the whole range. In addition, three-phase, solid phenol-phenol-rich liquid-nitrogen gas, equilibrium line for the phenol-nitrogen system was also determined at the temperature range of 313.4-314.0 K and pressure range of 1.0-180.4 bar and showed a temperature minimum at 313.4 K. No clathrate phase was found in this system. (C) 1997 Elsevier Science B.V
Phase equilibria of methane and carbon dioxide hydrates in the aqueous MgCl2 solutions
No full textThe ternary water + MgCl2 + CH4 phase equilibria were determined at the MgCl2 concentration ranges of 3-15 wt.% and at temperature and pressure ranges of 272-286 K and 30-130 bars, respectively. The ternary water + MgCl2 + CO2 phase equilibria are also determined at the MgCl2 concentration ranges of 3-10 wt.% and at the temperature and pressure ranges of 272-282 K and 15-45 bars, respectively. The quadruple points of the water + MgCl2 + CO2 system where the four phases, hydrate, water-rich liquid, CO2-rich liquid, and vapor phases, coexist were also carefully measured and found to be located just below the vapor pressure curve of pure carbon dioxide. For the prediction of hydrate phase equilibria, the vapor and liquid phases were treated with the Redlich-Kwong-Soave equation of state with the Modified Huron-Vidal second order mixing rule and the hydrate phase with the van der Waals-Platteeuw model. The Fitter-based model was adopted to estimate the activity of water in the aqueous electrolyte solution. This predictive approach was found to be well applicable to hydrate systems containing various concentrations of electrolytes. (C) 1998 Elsevier Science B.V. All rights reserved.This study is supported in part by non-directed research fund of Korean Science and Engineering Foundation
Experimental measurement of clathrate phase equilibria containing carbon dioxide, methane, phenol and p-cresol
No full text
Correlation of the vapor-liquid equilibria of CFC, HCFC and FC mixtures: Critical evaluation of mixing rules
No full textThe vapor-liquid equilibrium data of the binary CFC, HCFC, and FC mixtures were correlated with the Soave-Redlich-Kwong equation of state incorporated with some types of mixing rules; the conventional one fluid, Panagiotopoulos-Reid and modified Huron-Vidal second order mixing rules. The Panagiotopoulos-Reid mixing rule showed the superiority to the other models in predicting the VLE of freon mixtures with low errors. The modified Huron-Vidal second order model showed good convergence ability, which was due to its robustness to parameter variation.The authors gratefully acknowledge that this paper was support-ed by the fund of Korea Institute of Science and Engineering Foundation
- …
