Equilibrium Conditions for Semiclathrate Hydrates Formed with CO2, N2, or CH4 in the Presence of Tri-n-butylphosphine Oxide

2014

Ind. Eng. Chem. Res.

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This paper reports the experimentally measured phase equilibrium conditions for the clathrate hydrates formed from simulated mine ventilation air (0.50 vol% CH 4 + 99.50 vol% air) in the presence of 0, 5, 20, 37.1 and 50 wt% of Tetrabutylphosphonium Bromide (TBPB).These equilibrium conditions were measured at the temperature range of (281.62 to 292.49) K and pressure range of (1.92 to 18.55) MPa by using an isochoric equilibrium step-heating pressure search method. The results showed that addition of TBPB allowed the hydrate dissociation condition for mine ventilation air to become milder and at a given temperature, the lowest hydrate dissociation pressure was achieved at 37.1 wt% TBPB, corresponding to the stoichiometric composition for TBPB·32H 2 O. For each TBPB concentration tested, the semilogarithmic plots of hydrate dissociation pressure versus reciprocal absolute temperature can be satisfactorily fitted to two straight lines intersecting at 6.5 MPa. The slopes of these fitted straight lines are indifferent to changes in TBPB concentration. Gas composition analysis by gas chromatography also found that in the presence of 37.1 wt% TBPB, CH 4 could be enriched approximately 3.5-fold in the hydrate phase.

“…34 Figure 1 shows a typical pressure-temperature trace (for 5 wt% TBPB solution + MVA SCH), from which the dissociation point was determined to be 288.51 K and 18.39 MPa.…”

Section: Methodsmentioning

confidence: 99%

“…34 Briefly, a home-made non-visual 102 ml stainless steel cylindrical vessel with inside diameter of 38 mm and inside depth of 90 mm was used as the hydrate reactor. The reactor was immersed in a liquid bath, which was connected to a temperature control circulator (Haake A25).…”

Section: Experimental Apparatusmentioning

confidence: 99%

Phase Equilibria and Methane Enrichment of Clathrate Hydrates of Mine Ventilation Air + Tetrabutylphosphonium Bromide

2014

Ind. Eng. Chem. Res.

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“…The reliability and accuracy of our experimental system have been described in our recent work [47]. In the present work, the phase equilibrium conditions of flue gas + water are tabulated in Table 3 and plotted in Figure 2.…”

Section: Resultsmentioning

confidence: 93%

“…The schematic diagram of the experimental apparatus and its details can be found elsewhere [47,48]. Briefly, the high pressure reactor used in the present work was a home-made non-visual 102 ml stainless steel cylindrical vessel with inside diameter of 38 mm and depth of 90 mm.…”

Section: Experimental Apparatusmentioning

confidence: 99%

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

The Journal of Chemical Thermodynamics

2015

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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.

“…Addition of thermodynamic promoters such as TBAB [27], tetra-butyl ammonium nitrate (TBANO 3 ) [14], TBPB [28], tetra-amyl ammonium chloride (TAAC) [29] and TBPO [30] …”

Section: Introductionmentioning

confidence: 99%

Thermodynamic stability conditions, methane enrichment, and gas uptake of ionic clathrate hydrates of mine ventilation air

Chemical Engineering Journal

2015

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Abatement of methane from mine ventilation air (MVA) is a significant challenge faced by coal mining industry. A promising method for methane capture from gas mixture is clathrate hydrate formation. In search of suitable and costeffective low-dosage promoters for hydrate-based methane capture processes, this paper reports the pressure requirement for the hydrate formation of simulated MVA (0.5 vol% CH 4 + 99.5 vol% air) and its potential for methane extraction, in the presence of tri-n-butyl phosphine oxide (TBPO) or tetra-n-butyl ammonium bromide (TBAB) at three different initial loadings (5 wt%, 15 wt%, and 26 wt%). An isochoric equilibrium step-heating pressure search method was used to measure the hydrate phase equilibrium conditions at the temperature range of (277.61 to 295.54) K and pressure range of (0.23 to 19.11) MPa. It was found that at a given initial loading, TBPO was largely more effective than TBAB in reducing the pressure requirement for hydrate formation of MVA. At a given temperature, the equilibrium pressures of the clathrate hydrates were indifferent to the change in the initial loading of TBPO from 5 wt% to 26 wt%, in contrast to those of TBAB. Gas composition analysis by gas chromatography confirmed that CH 4 could be significantly enriched in the ionic clathrate hydrates, and the highest methane enrichment ratio obtained in the present work was 300%, with TBPO at initial loading of 5 wt%. At this relatively low loading, within a given period of 5 hours, TBPO also led to higher gas uptake compared with TBAB. The advantages of TBPO as a promoter of MVA hydrate were discussed.