Liquid phase characterization of multicomponent gas hydrate systems
Bibliographic record
Abstract
This thesis characterizes the liquid phase of several multicomponent gas hydrate systems during growth and equilibrium through mole fraction measurements. To demonstrate the importance of the liquid phase in gas hydrate equilibrium modeling, both liquid and gas phases of the CO2+CH4+H2O system were modeled using various equation of states. It was found that the mole fraction where both liquid and gas fugacities met at equilibrium is highly dependent on the liquid phase when compared to the gas phase. Furthermore, liquid and gas phase compositions at three-phase equilibrium (hydrate-liquid-vapor) were generated using modified interaction parameters. If interaction parameters were optimized using only liquid mole fraction data, both gas and liquid equilibrium compositions were successfully generated. Conversely, both phases could not be adequately modeled when interaction parameters were optimized using only vapor data; successful results were limited to the vapor phase. These findings are likely due to non-ideal effects present in the liquid phase but absent in the gas phase. Solubility isotherm trends for the N2+CO2+H2O and CH4+C2H6+H2O systems were experimentally obtained. As simple nitrogen systems favor structure II and simple carbon dioxide systems structure I, their combination yields a system where a structure change transition occurs depending on the relative amount of gas. In the case of the methane and ethane mixture, both individual simple systems favor structure I while their mixture can form structure II under certain conditions. This phenomenon is the result of structure II offering a specific ratio of large and small cavities that is only favorable for specific ranges of methane and ethane concentrations. The solubility trends obtained of both multicomponent systems were found to shift where a structure change is reportedly occurring; a novel find. This can be explained by the fact that guest occupancies and hence solid phase mole fractions differ for each structure. Replicates obtained near the conditions where a structure change is reportedly occurring were found to vary. This fluctuation was the consequence of both structures being present in various ratios during sampling, even if only one structure is thermodynamically favored. Liquid and gas mole fractions were experimentally acquired during growth for the CH4+CO2+H2O system. Constant gas phase compositions along with controlled pressure and temperature enabled a consistent differential pressure between operating conditions and the equilibrium plane during kinetic experiments. Similar to results obtained in literature for simple hydrate systems, both methane and carbon dioxide liquid mole fractions were found independent of time. Overall growth rates were obtained and had a linear relationship with time. Liquid mole fractions obtained during induction revealed that methane is consumed significantly more than carbon dioxide during the early stages of growth.
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How this classification was reachedexpand
Full frame machine prediction
Teacher imitationNot calibrated prevalence, not ground truth. Human validation pending. The Gemma side is a direct model label for every work in the frame, read from the title-only record. The Codex side is a classifier learned from the 10,348 direct Codex labels and calibrated to design-weighted sample rates; fields without enough sample support carry no Codex call. Candidate is the union of the two sides; consensus is their intersection. These outputs are machine_predicted_unvalidated and are not human labels.
Distilled classifier scores by category (both heads)
| Category | Codex | Gemma |
|---|---|---|
| Metaresearch | 0.000 | 0.000 |
| Meta-epidemiology (narrow) | 0.000 | 0.000 |
| Meta-epidemiology (broad) | 0.000 | 0.000 |
| Bibliometrics | 0.001 | 0.000 |
| Science and technology studies | 0.000 | 0.000 |
| Scholarly communication | 0.000 | 0.001 |
| Open science | 0.000 | 0.000 |
| Research integrity | 0.000 | 0.000 |
| Insufficient payload (model declined to judge) | 0.001 | 0.000 |
Machine scores (provisional)
The two teacher heads of the student model, read on this work. A score orders the frame for review; it never asserts a category, and the validation status ships verbatim with every row.
Baseline scores from an immature model (maturity gate not passed, 7 training rounds). Scores rank; they never assert a category.
score_only:v0-immature-baseline · verbatim from the scoring run: score_only means the number may rank works, and no category label ships from itClassification
machine, unvalidatedMachine predicted; a candidate call from one source (direct Gemma or distilled Codex), not a consensus.
How this classification was reached, model by model and score by score, is at the end of the page under "How this classification was reached".