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Experimental Study on the Dissociation Equilibrium of (CH4 + CO2 + N2) Hydrates in the Mixed Sediments
journal contribution
posted on 2019-11-19, 16:05 authored by Liang Mu, Qingyan CuiThe recovery of CH4 from gas hydrate by injecting
flue
gas would inevitably lead to coexistence of CH4, CO2, and N2 in the hydrate phase. To simulate the
actual situation and investigate the stability condition of (CH4 + CO2 + N2) hydrates, their dissociation
equilibrium in the mixed sediments of quartz sand and kaolin clay
was measured with the isochoric pressure search method. Six gas samples
were tested and analyzed with respect to the CH4 content
and the mole ratio of CO2/N2 in the gas phase.
The results indicated that the hydrate dissociation equilibrium pressure
at a given temperature shows a decreasing trend as the CH4 content increases at a lower CO2/N2 ratio,
which was contrary to that at a higher CO2/N2 ratio. The dissociation equilibrium temperature of (CH4 + CO2 + N2) hydrates for the mixed sediments
is shifted lower than those for bulk phase at the same pressure. The
effect of the mixed sediment composition and water saturation on the
hydrate dissociation equilibrium was investigated. The results showed
that the temperature shift increases with the increase of kaolin content
in the mixed sediments, while it decreases as the water saturation
increases. The maximum temperature shift observed in this work was
1.56 K in the mixed sediments (the mass ratio quartz sand and kaolin
clay was 1:0.20) with a water saturation of 20%. The hydrate dissociation
enthalpies are calculated with the Clausius–Clapeyron equation.
It was observed that the hydrate dissociation enthalpies exhibited
a decreasing trend with the increase of CH4 content in
the gas phase.
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temperature shift increaseswater saturation increasesN 2sedimentwater saturationCH 4isochoric pressure search methodCO 2gas phaseCH 4 contenthydrate dissociation equilibrium pressurehydrate dissociation equilibriumdissociation equilibrium temperaturekaolin clayCH 4 content increaseshydrate dissociation enthalpiesmass ratio quartz sand
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