Phase equilibria and methane enrichment of clathrate hydrates of mine ventilation air + tetrabutylphosphonium bromide

• Published in: Industrial & Engineering Chemistry Research
• Main Authors: Du, Jianwei, Li, Huijuan, Wang, Liguang
• Format: Article in Journal/Newspaper
• Language: English
• Published: American Chemical Society 2014
• Subjects: Ventilation air; Gas hydrate; Gas separation; Methane hydrate; 1500 Chemical Engineering; 1600 Chemistry; 2209 Industrial and Manufacturing Engineering
• Online Access: https://espace.library.uq.edu.au/view/UQ:328901/lwang2_iecr.pdf; https://espace.library.uq.edu.au/view/UQ:328901

This paper reports the experimentally measured phase equilibrium conditions for the clathrate hydrates formed from simulated mine ventilation air (0.50 vol % CH + 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 281.62-292.49 K and pressure range of 1.92-18.55 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 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 could be enriched approximately 3.5-fold in the hydrate phase.