Search

• Experimental study on inhibition of gas hydrate formation for CO 2 separation. • Develop a chemical affinity model to predict CO 2 hydrate formation. • Optimal inhibitory compound system is 15 mg/mL glucose + 1.00 mg/ml attapulgite. • Induction time of hydrate formation is extended by approximately 122% • Gas consumption is reduced by 23.72% to improve the inhibitory effect. Natural gas and water can form complex cage crystals in oil and gas pipelines under certain conditions. The natural gas hydrate formed after crystal clustering can block the pipeline and affect the operation efficiency of the pipeline, and even cause equipment damage, bringing economic and security problems to enterprises. In the present study, we experimentally investigated the inhibition of CO 2 formation hydrate using attapulgite (ATP) and glucose (GLC). The kinetic influence on the formation of CO 2 hydrate by the complex pairing of kinetic inhibitor ATP is conducted under the working conditions of 277.15 K and 3.5 MPa. The effect of compound inhibitors on the temperature and pressure conditions, growth process and gas consumption of hydrate formation are revealed. The chemical affinity model of CO 2 hydrate formation under a compound inhibitor system is derived and established based on experimental studies. The results show that the combination of GLC and ATP can inhibit the formation of CO 2 hydrate to varying degrees, prolong the induction time of hydrate, and reduce the consumption of CO 2. The optimized experimental studies demonstrate that the best inhibitory compound system is 15 mg/mL GLC + 1.00 mg/mL ATP. Compared with the pure water system and single 15 mg/mL GLC system, the induction time is extended by 122.61% and 122.23%, while the gas consumption is reduced by 23.72% and 3.41%. The results provide new ideas and methods for the prediction of hydrate formation in the compound inhibitor system for the safe operation of oil and gas pipelines. [ABSTRACT FROM AUTHOR]

The gas-liquid two-phase flow within a double inlet cyclone for natural gas separation was numerically simulated using the discrete phase model. The numerical approach was validated with the experimental data, and the comparison results agreed well with each other. The simulation results showed that the strong swirling flow produced a high centrifugal force to remove the particles from the gas mixture. The larger particles moved downward on the internal surface and were removed due to the outer vortex near the wall. Most of the tiny particles went into the inner vortex zones and escaped from the up-outlet. The swirling flow was concentric due to the design of the double inlet for the cyclonic separator, which greatly improved the separating efficiency. The separating efficiency was greater than 90% with the particle diameter of more than 100 μm. [ABSTRACT FROM AUTHOR]

The Volume of Fluid method and Re-Normalisation Group (RNG) k-ε turbulence model were employed to predict the gas-liquid two-phase flow in a terrain-inclined pipeline with deposited liquids. The simulation was carried out in a 22.5 m terrain-inclined pipeline with a 150 mm internal diameter. The flow parameters were numerically analyzed in detail including the phase distribution in pipes, the velocity and pressure around the elbow, the liquid flow rate and liquid holdup in different cross-section and the volume of liquid outflow. The numerical results presented that a wave crest formed on the liquid level under the suction force which caused by the negative pressure around the elbow, and then it touched to the top of the pipe. When the liquid blocked the pipe, the pressure drop between the upstream and downstream of the elbow increased with the increase of the gas velocity. At larger gas velocity, more liquid was carried out of the pipeline. The liquid periodically flowed and returned along the uphill section when the liquid was no longer flowing out of the pipeline. [ABSTRACT FROM AUTHOR]

The supersonic separation is a novel technology in the natural gas dehydration for its compact design and fewer emissions. The other fascinating advantage is that the diffuser can convert kinetic energy into pressure energy to improve the energy efficiency. The mechanism of the pressure recovery is not well understood for the various flow conditions in supersonic velocities. The maximum pressure recovery coefficient (PRC) was estimated in theory and a theoretical equation was obtained with the ideal gas assumption. The theoretical results indicated that the PRC depended on the gas adiabatic exponent and Mach number in the upstream of the shock wave. A computational fluid dynamics model was developed to evaluate the gas dynamic parameters with various Mach numbers and their effects on the PRC. We found that a higher adiabatic exponent induced a larger PRC when the gas Mach number is more than 1.3. The PRC declined with the increase of the Mach number in the upstream of the shock wave both in the theoretical and numerical predictions. The numerical results are smaller than the ideal data with the maximum error of about 8.69% in the whole computed gas Mach number from 1.15 to 1.87. These results have suggested that the derived theoretical equation can be employed to estimate the PRC in the supersonic separation process to improve the design efficiency. [ABSTRACT FROM AUTHOR]

A supersonic separator has been introduced to remove water vapour from natural gas. The mechanisms of the upstream and downstream influences are not well understood for various flow conditions from the wellhead and the back pipelines. We used a computational model to investigate the effect of the inlet and outlet flow conditions on the supersonic separation process. We found that the shock wave was sensitive to the inlet or back pressure compared to the inlet temperature. The shock position shifted forward with a higher inlet or back pressure. It indicated that an increasing inlet pressure declined the pressure recovery capacity. Furthermore, the shock wave moved out of the diffuser when the ratio of the back pressure to the inlet one was greater than 0.75, in which the state of the low pressure and temperature was destroyed, resulting in the re-evaporation of the condensed liquids. Natural gas would be the subsonic flows in the whole supersonic separator, if the mass flow rate was less than the design value, and it could not reach the low pressure and temperature for the condensation and separation of the water vapor. These results suggested a guidance mechanism for natural gas supersonic separation in various flow conditions. [ABSTRACT FROM AUTHOR]