Gas hydrate formation was studied in a new apparatus designed to accommodate three different size volume beds of silica sand particles. The sand particles have an average diameter equal to 329 μm. The hydrate was formed in the water, which occupied the interstitial space of the water-saturated silica sand bed. A bulk gas phase was present above the bed (gas cap). Gas uptake measurements were carried out during experiments at constant temperature. More than 74.0% of water conversion to hydrate was achieved in all experiments conducted with methane at 4.0 and 1.0 °C. An initial slow growth was followed by a rapid hydrate growth rate of equal magnitude for nearly all experiments until 43-53% of water was converted to hydrate. During the third and final growth stage, the final conversions were between 74 and 98% and the conversion dynamics changed. Independent verification of hydrate formation in the sand was achieved via Raman spectroscopy and morphology observations in experiments using the same sand/water system.
The decomposition of methane hydrate crystals formed in sediment at 1.0, 4.0, and 7.0 °C was studied in a new apparatus designed to accommodate three different size volume beds of silica sand particles. The sand particles are microporous with a 0.9 nm pore diameter and have an average diameter equal to 329 μm. The hydrate was formed in the interstitial spaces between sand particles, and the hydrate crystal decomposition was driven by heating (thermal stimulation). The amount of methane released from the dissociating hydrate in each experiment (methane recovery curve) was determined, and it was shown that the release of gas proceeds in two stages in terms of rate. The rate of methane release (recovery) per mole of water depends on the bed size for the first stage of hydrate dissociation. The second stage rate does not depend on the bed size. This work suggests that the comparison of simulated data to experimental results from laboratory synthesized hydrate and possibly from natural samples should be done with more than one sample-size data.
The separation and capture process of carbon dioxide from power plants is garnering interest as a method to reduce greenhouse gas emissions. In this study, aqueous alkanolamine solutions were studied as absorbents for CO 2 capture. The solubility of CO 2 in aqueous alkanolamine solutions was investigated with a continuous stirred reactor at 313, 333 and 353 K. Also, the heat of absorption (−ΔH abs ) between the absorbent and CO 2 molecules was measured with a differential reaction calorimeter (DRC) at 298 K. The solubility and heat of absorption were determined at slightly higher than atmospheric pressure. The enthalpies of CO 2 absorption in monoethanolamine (MEA), diethanolamine (DEA), triethanolamine (TEA), and 2-amino-2-methyl-1-propanol (AMP) were 88.91, 70.44, 44.72, and 63.95, respectively. This investigation showed that the heat of absorption is directly related to the quantity of heat for absorbent regeneration, and is dependent on amine type and CO 2 loading.
For 5.0, 20.5, 50.0, and 75.0 mass % methyldiethanolamine (MDEA)
aqueous solutions, solubilities of
CO2 were measured at 323.15, 348.15, and 373.15 K,
respectively. Isothermal absorption capacities of
CO2 as a function of MDEA concentration are presented.
Lastly, the absorption enthalpy of CO2 in
50.0
mass % MDEA solution was calculated to be 54
kJ·mol-1 CO2.
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