The effect of experimental conditions on natural gas hydrate formation

Download

index.pdf

Date

2020

Author

Longinos, Sotirios

Metadata

Show full item record

This work is licensed under a Creative Commons Attribution-NonCommercial-NoDerivatives 4.0 International License.

Item Usage Stats

256
views

372
downloads

Natural gas hydrates (NGH) are proposed as gas storage and transportation media owing to their high gas content and long-term stability of hydrate crystal structure at common refrigeration temperatures and atmospheric pressure. Technically feasible, cost efficient hydrate production is one of the crucial items of the whole chain of storage and transportation of gas by means of NGH technology. This study investigated the effects of types of impellers and baffles, and the use of promoters on natural gas hydrate formation. Up-pumping pitched blade turbine (PBTU) and Rushton turbine (RT) were the two types of impellers tested. The reactor was equipped with different designs of baffles: full, half and surface baffles, or no baffles. In total 48 experiments were completed with different impeller – baffle combinations. Single (PBTU or RT), dual (PBTU/PBTU or RT/RT) and dual-mixed (PBTU/RT or RT/PBTU) use of impellers with full (FB), half (HB), surface (SB) and no baffle (NB) combinations formed two sets of 24 experiments. The first set was completed with the use of pure methane as hydrate forming gas and in the second set methane – propane mixture (95% - 5%) was used. Experimental data was analyzed in terms of induction time, hydrate formation rate, overall power consumption, hydrate productivity and conversion of water to hydrate. In addition, split fraction of methane and propane in free gas and solid hydrate during hydrate formation from mixture gas is determined. The reactor was operated in batch mode in all the experiments. Single impeller experiments with methane showed that Rushton turbine has better performance than up-pumping pitched blade turbine, for all kind of baffles. Use of dual impellers, either the same type or mixed, produced similar results of single impeller. The initial hydrate formation rate is generally higher with the use of Rushton turbine, but the decline rate of hydrate formation was also high compared to up-pumping pitched blade turbine (PBTU). The higher amount of hydrate formed at the gas-water interface initially restricts the mass transfer between gas and water phases and results in a higher decline in the formation rate of hydrate. The other fact causing the decline in hydrate formation rate is the exothermic nature of hydrate formation. Hydrate formation process by gas mixtures become more complex because of different partition of gas components in free gas and solid hydrate phases. Propane is consumed more if hydrate is formed from a gas mixture of methane – propane. This fact brings another complexity of varying hydrate equilibrium curve during hydrate formation. As propane is consumed, hydrate equilibrium pressure gets higher for the given process temperature. Aqueous solutions of amino acids tested in this study showed shorter induction time and generally higher hydrate formation rates compared to distilled water. This indicates a potential of finding hydrate promoters among these amino acids.

Subject Keywords

Natural gas, Natural gas Hydrates., Natural gas hydrates, rate of hydrate formation, induction time, amino acids.

URI

http://etd.lib.metu.edu.tr/upload/12625534/index.pdf
https://hdl.handle.net/11511/45752

Collections

Graduate School of Natural and Applied Sciences, Thesis

Suggestions

OpenMETU
Core

The effect of experimental conditions on methane hydrate formation by the use of single and dual impellers Longinos, Sotirios Nik; Parlaktuna, Mahmut (2021-02-01) Natural gas hydrates (NGH) are proposed as gas storage and transportation media owing to their high gas content and long-term stability of hydrate crystal structure at common refrigeration temperatures and atmospheric pressure. Technically feasible, cost efficient hydrate production is one of the crucial items of the whole chain of storage and transportation of gas by means of NGH technology. This study investigates the effects of types and number of impellers and baffles. Single impeller experiments showed...
Examination of behavior of lysine on methane (95%)-propane (5%) hydrate formation by the use of different impellers Longinos, Sotirios Nik; Parlaktuna, Mahmut (2021-03-01) Hydrate formation characteristics and hydrodynamic behavior have been investigated for mixture of methane-propane hydrate formation with pure water and with the amino acid of lysine 1.5 wt% at 24.5 bars and 2 degrees C. There were total 12 experiments with full and no baffle estimating the induction time, rate of hydrate formation, hydrate productivity and power consumption. The outcomes showed that radial flow experiments with radial flow have better behavior compared to mixed flow ones due to better inter...
Kinetic Analysis of Methane Hydrate Formation with Butterfly Turbine Impellers Longinos, Sotirios Nik.; Longinou, Dionisia Dimitra; Myrzakhmetova, Nurbala; Akimbayeva, Nazgul; Zhursumbaeva, Mariamkul; Abdiyev, Kaldibek; Toktarbay, Zhexenbek; Parlaktuna, Mahmut (2022-07-01) Heat generation during gas hydrate formation is an important problem because it reduces the amount of water and gas that become gas hydrates. In this research work, we present a new design of an impeller to be used for hydrate formation and to overcome this concern by following the hydrodynamic literature. CH4 hydrate formation experiments were performed in a 5.7 L continuously stirred tank reactor using a butterfly turbine (BT) impeller with no baffle (NB), full baffle (FB), half baffle (HB), and surface b...
The effect of gas production from deeper conventional gas reservoirs on shallower gas hydrate layer stability: A case study in the conditions of the Sakarya gas field, Western Black Sea Aydın, Hakkı; Merey, Şükrü (Elsevier BV, 2021-6) Gas hydrate deposits are generally found in the shallow deepwater regions where continuous permafrost exists. The presence of water, methane and thermodynamic conditions (low temperature and high pressure) is critical for gas hydrate accumulation. Disturbing thermodynamic conditions such as depressurizing and thermal treatment are the primary processes for gas hydrate dissociation. In this study, we investigate the stability of a shallow depth gas hydrate layer in the conditions of conventional gas producti...
Evaluation of limestone incorporated cement compositions for cementing gas hydrate zones in deepwater environments Hıdıroğlu, İnanç Alptuğ; Parlaktuna, Mahmut; Yaman, İsmail Özgür; Department of Petroleum and Natural Gas Engineering (2017) One of the potential problems which must be overcome during oil or gas exploration in deepwater environments is to complete the drilling operations without decomposing the gas hydrates. Gas hydrates remain stable as long as the thermodynamic conditions are not changed. But, especially by increasing temperature during drilling operations, there is always a possibility of change in thermodynamic conditions, which will cause decomposition. Another factor which may disturb the thermodynamic conditions is the ev...

Citation Formats

S. Longinos, “The effect of experimental conditions on natural gas hydrate formation,” Thesis (Ph.D.) -- Graduate School of Natural and Applied Sciences. Petroleum and Natural Gas Engineering., Middle East Technical University, 2020.