Formation Kinetics of Propane Hydrates

Abstract

Propane hydrates are rarely considered by scientists. Despite the narrow borders of the formation region, they can form during storage and transportation of the liquefied petroleum gases. Therefore, it is important to know the induction time for solid hydrate formation. The present paper has considered the formation both from melting ice (at 1 °C and 4 bar) and from water (at 2 °C and 3.6-4.8 bar) in a stirred vessel. The formation from ice was quite instantaneous, while the production from water took about 15 h to start (and about 3 days to be completed) and depended on the pressure: in fact, it was slower at low pressure. All hydrates contained a high amount of ice (75-80%). The modulated differential scanning calorimetry was used for hydrate characterization: the reversing (heat-capacity) curves permitted one to quickly distinguish between hydrate and ice, also allowing a semiquantitative evaluation of the hydrate content.

Modelling of hydrate formation kinetics: State-of-the-art and future directions

“…Skovborg et al (1993) attributed these results to the observation of a more ordered and rigid structure in the liquid phase as its temperature approaches the freezing temperature of water, which favours hydrate formation, since it can serve as a 'template' for the hydrate structure to be formed. In perfect agreement with this reasoning, Giavarini et al (2003) verified an almost immediate formation of propane hydrate from melting ice (T op = 1 • C, P op = 4 bar) but a much slower process (13.3 t nuc (h) 18) when liquid water was employed in the reactor (T op =2 • C, P op =3.6.4.8 bar). Similar trends of an effect Table 2 Induction time for methane hydrates formed from water with different previous treatments (Vysniauskas and Bishnoi, 1983) of the thermal history of water upon the nucleation time were reported by many authors (Schroeter et al, 1983;Monfort and Nzihou, 1993;Parent and Bishnoi, 1996;Moudrakovski et al, 2001;Link et al, 2003;Lee et al, 2005a,b;Servio and Englezos, 2003;Linga et al, 2007), characterising what has been known as the memory effect in hydrate nucleation.…”

“…A slight increase in the operating temperature of jacketed reactors during hydrate growth has already been reported by some investigators (Giavarini et al, 2003;Zhong and Rogers, 2000;Karaaslan et al, 2002;Tsuji et al, 2004;Lee et al, 2005aLee et al, , 2007Linga et al, 2007). Zhang et al (2004), in particular, demonstrated the existence of a clear correlation between the temporal evolution of the gas consumption rate and the operating temperature in the reactor for their data.…”

Reaction rate constant of CO2 hydrate formation and verification of old premises pertaining to hydrate growth kinetics

“…In addition, the Zetasizer Nano ZS contains an internal cooling device to maintain the desired operating temperature inside the cell. Hydrates are formed in the 600 cm 3 internal volume stainless steel crystallizer (12,000 kPa pressure rating). A PPI DYNA/ MAG MM-006 mixer (0-2,500 rpm) has been mounted on top of the crystallizer to ensure sufficient mixing.…”

Recent advances in gas hydrate-based CO2 capture

“…Propane alone forms S II hydrates at 275 K and between 0.36 MPa and 0.48 MPa (Giavarini et al, 2003;Hendriks et al, 1996). It induces the formation of S II hydrates when it competes with CO 2 for occupancy of large cages (Adisasmito and Sloan, 1992).…”