Oil Gas Separation Research Articles

Investigation on the oil–gas separation efficiency considering oil droplets breakup and collision in a swirling flow

In this study, the oil droplets separation process in a swirling flow was investigated using numerical simulations and verification experiments. Numerical models were established to investigate the effects that the collision and breakup of droplets and the collision between droplets and wall on separation efficiency, respectively. The separation efficiencies were calculated using different models under various inlet velocities, from 10 to 18m/s. The simulated results showed that droplets colliding could improve the separation efficiencies with up to 22.4% increments at the 10m/s inlet velocity for droplets with a diameter of 10μm. The oil–gas separation efficiency was reduced up to 17.4% due to the oil droplet–wall interaction in swirling flow when the simulation model involved droplet–wall collisions. The simulated separation efficiencies showed little change when oil droplet breakups were considered in the model under different inlet velocities and droplet diameters. A test rig was built to validate the simulation results. It showed good agreement between the experimental data and simulated results. Thus, the numerical simulation model could be used to predict separation performance and understand the separation process in a swirling flow.

FCC riser quick separation system: a review

The riser reactor is the key unit in the fluid catalytic cracking (FCC) process. As the FCC feedstocks become heavier, the product mixture of oil, gas and catalysts must be separated immediately at the outlet of the riser to avoid excessive coking. The quick separation system is the core equipment in the FCC unit. China University of Petroleum (Beijing) has developed many kinds of separation system including the fender-stripping cyclone and circulating-stripping cyclone systems, which can increase the separation efficiency and reduce the pressure drop remarkably. For the inner riser system, a vortex quick separation system has been developed. It contains a vortex quick separator and an isolated shell. In order to reduce the separation time, a new type of separator called the short residence time separator system was developed. It can further reduce the separation time to less than 1 s. In this paper, the corresponding design principles, structure and industrial application of these different kinds of separation systems are reviewed. A system that can simultaneously realize quick oil gas separation, quick oil gas extraction and quick pre-stripping of catalysts at the end of the riser is the trend in the future.

Conceptual Design of an Oil Shale Comprehensive Refinery Process with High Resource Utilization

With the decrease of conventional energy reserves, countries such as China began to explore efficient ways to use oil shale as an alternative energy source. The refinery technology used for oil shale is retorting. However, in this process, fine-particle shale, semi-coke, and retorting gas are not used efficiently; rather, they are dismissed as solid and gaseous wastes. Resource utilization is extremely low in retorting. In addition, the price of crude retorting oil is very low, making the whole retorting process suffer from a low economic benefit. In this paper, a new oil shale comprehensive refinery process is proposed, aiming to process shale particles from all ranges of sizes. The new process includes a gas circulation shale retorting unit, a Dagong shale retorting unit, an oil–gas separation unit, a retorting gas steam reforming unit for hydrogen production, and a shale oil hydrogenation unit. Fine-particle shale from the gas circulation shale retorting unit is used as raw material in the Dagong shale...

Self-similarity and scaling transitions during rupture of thin free films of Newtonian fluids

Rupture of thin liquid films is crucial in many industrial applications and nature such as foam stability in oil-gas separation units, coating flows, polymer processing, and tear films in the eye. In some of these situations, a liquid film may have two free surfaces (referred to here as a free film or a sheet) as opposed to a film deposited on a solid substrate that has one free surface. The rupture of such a free film or a sheet of a Newtonian fluid is analyzed under the competing influences of inertia, viscous stress, van der Waals pressure, and capillary pressure by solving a system of spatially one-dimensional evolution equations for film thickness and lateral velocity. The dynamics close to the space-time singularity where the film ruptures is asymptotically self-similar and, therefore, the problem is also analyzed by reducing the transient partial differential evolution equations to a corresponding set of ordinary differential equations in similarity space. For sheets with negligible inertia, it is shown that the dominant balance of forces involves solely viscous and van der Waals forces, with capillary force remaining negligible throughout the thinning process in a viscous regime. On the other hand, for a sheet of an inviscid fluid for which the effect of viscosity is negligible, it is shown that the dominant balance of forces is between inertial, capillary, and van der Waals forces as the film evolves towards rupture in an inertial regime. Real fluids, however, have finite viscosity. Hence, for real fluids, it is further shown that the viscous and the inertial regimes are only transitory and can only describe the initial thinning dynamics of highly viscous and slightly viscous sheets, respectively. Moreover, regardless of the fluid’s viscosity, it is shown that for sheets that initially thin in either of these two regimes, their dynamics transition to a late stage or final inertial-viscous regime in which inertial, viscous, and van der Waals forces balance each other while capillary force remains negligible, in accordance with the results of Vaynblat, Lister, and Witelski.

A Honeycomb-Structured Ti-6Al-4V Oil–Gas Separation Rotor Additively Manufactured by Selective Electron Beam Melting for Aero-engine Applications

Oil–gas separation is a key process in an aero-engine lubrication system. This study reports an innovative development in oil–gas separation. A honeycomb-structured rotor with hexagonal cone-shaped pore channels has been designed, additively manufactured from Ti-6Al-4V using selective electron beam melting (SEBM) and assessed for oil–gas separation for aero-engine application. The Ti-6Al-4V honeycomb structure showed a high compressive strength of 110 MPa compared to less than 20 MPa for metal foam structures. The oil–gas separation efficiency of the honeycomb-structured separation rotor achieved 99.8% at the rotation speed of 6000 rpm with much lower ventilation resistance (17.3 kPa) than that of the separator rotor constructed using a Ni-Cr alloy foam structure (23.5 kPa). The honeycomb-structured Ti-6Al-4V separator rotor produced by SEBM provides a promising solution to more efficient oil–gas separation in the aero-engine lubrication system.

Downhole CO2 partial pressure calculation and tubing material selection – a case study of an offshore oil field in the South China Sea

Purpose This paper aims to establish the downhole CO2 partial pressure profile calculating method and then to make an economical oil country tubular goods (OCTG) anti-corrosion design. CO2 partial pressure is the most important parameter to the oil and gas corrosion research for these wells which contain sweet gas of CO2. However, till now, there has not been a recognized method for calculating this important value. Especially in oil well, CO2 partial pressure calculation seems more complicated. Based on Dolton partial pressure law and oil gas separation process, CO2 partial pressure profile calculating method in oil well is proposed. A case study was presented according to the new method, and two kinds of corrosion environment were determined. An experimental research was conducted on N80, 3Cr-L80 and 13Cr-L80 material. Based on the test results, 3Cr-L80 was recommended for downhole tubing. Combined with the field application practice, 3Cr-L80 was proved as a safety and economy anti-corrosion tubing material in this oil field. A proper corrosion parameter (mainly refers to CO2 partial pressure and temperature) can ensure a safety and economy downhole tubing anti-corrosion design. Design/methodology/approach Based on Dolton partial pressure law and oil gas separation process, CO2 partial pressure profile calculating method in oil well is proposed. An experimental research was conducted on N80, 3Cr-L80 and 13Cr-L80 material. A field application practice was used. Findings It is necessary to calculate the CO2 partial pressure properly to ensure a safety and economy downhole tubing (or casing) anti-corrosion design. Originality/value The gas and oil separation theory and corrosion theory are combined together to give a useful method in downhole tubing anti-corrosion design method.

Crude oil foams. Part 1 – A novel methodology for studying non-aqueous foams formed by depressurization

Crude oil foams are highly complex non-aqueous foams that tend to form from the release of dissolved gas after an abrupt decrease in the pressure. These foams are typically encountered during crude oil exploitation and refining and especially in oil–gas separation processes. These kinds of foams are widely different from aqueous ones in terms of formation and stabilization and therefore classical methods developed for the study of aqueous foams are no longer useful to reproduce crude oil foam formation conditions. For this reason, we have developed a foam test based on crude oil depressurization to simulate crude oil formation during oil production. Foams can be generated through the laboratory test in a reproducible way and can be consequently characterized in terms of foaminess, stability and kinetics of rupture. Moreover, we also have developed a new methodology to characterize foam stability and liquid foaminess by modeling the crude oil defoaming kinetics. The model we propose allows an easy comparison of the behavior of crude oils foams. By studying different crude oils of known compositions, we have found a correlation between their behavior in term of stability and foaminess and a parameter that takes into account the crude viscosity and its composition.

The design and performance evaluation of axial ventilator with honeycomb in the turbofan engine lubrication system

Numerical simulations have been carried out to investigate the performance of the axial ventilator equipped with honeycomb structure. The oil /air two-way coupling model based on the Realizable k–ɛ turbulence model and the droplet impact model are proposed. Based on verifying the rationality of numerical model, characteristics of flow resistance and oil–gas separation efficiency are calculated and analyzed. The results show that the axial ventilator with honeycomb has favorable separation efficiency, which is estimated as 99.6% for the oil droplet diameter of 5 µm. The honeycomb structure has little effect on flow resistance, but plays a major role in the oil–gas separation of axial ventilator, where the contribution to the oil separation accounts for 80% at least. Besides, the increase of rotation Reynolds number enhances the centrifugal force, resulting in the increase of separation efficiency, while the increase of nondimensional mass flow rate and environmental temperature reduce the residence time of oil droplets in the axial ventilator mainly, resulting in the decreasing of separation efficiency.

Highly Sensitive Dissolved Hydrogen Sensor Based on Side-Polished Fiber Bragg Grating

To eliminate the time-consuming oil-gas separation process in online dissolved gas detection of power transformer, fiber Bragg grating (FBG)-based hydrogen sensor is proposed to be installed into the power transformer oil directly. In the sensor design, the FBG cladding is side-polished with a residual thickness of 20 μm and sputtered with palladium/silver. Since side-polished cladding is very sensitive to curvature strain induced by palladium in the presence of dissolved hydrogen, the proposed sensor is much more sensitive than the untreated FBG hydrogen sensor. Measurements prove that the sensitivity is as high as 0.477 (pm/(μL/L)), about 11.4 times higher than the conventional FBG hydrogen sensor. Furthermore, repeatability and short-term stability have been investigated. The performances satisfy the actual need of monitoring dissolved hydrogen concentration in power transformer oil.

Analysis of Plastic Oil-Gas Separator for Diesel Engine Valve Chamber Cover

Three different configurations of plastic oil-gas separator for diesel engine valve chamber cover were studied using numerical simulations. The distribution of flow velocity, pressure and oil droplets collection from simulation results were assessed to find out an optimum design for the oil-gas separator. Further, the oil-gas separation efficiency from simulation and experimental test was also reviewed to verify the simulation model as well as selection of the best design amongst the considered three configurations of the oil-gas separator.

Nonlinear model predictive control using trust-region derivative-free optimization

Gradient-based optimization may not be suited if the objective and constraint functions in a nonlinear model predictive control (NMPC) optimization problem are not differentiable. Some well-known derivative-free optimization (DFO)-algorithms are investigated, and a novel warm-start modification to the Wedge DFO-algorithm is proposed. Together with a gradient-based SQP-algorithm these are applied to the NMPC problem and compared in a single-shooting NMPC formulation to a subsea oil–gas separation process. The findings are that DFO is significantly more robust against the numerical issues, compared to a gradient-based SQP tested. Moreover, the warm-start modification reduces the computational complexity.

Energy Saving Measures of Oil and Gas Gathering System in Changqing Low Permeable Oilfield

Because of its property of low permeability, low pressure and low production, Changqing low permeable oilfield decreases rapidly in the initial potential stage and has low individual-well producing rate, which give rise to the overestimated oilfield production and large-scale ground construction project of gathering system. Eventually, the problem of “big Marathi car” in oil gathering system generated excessive energy consumption. It is multi-purpose station, pumping station and block station that turn out to be the main energy consumption point, which consume over 90% of system electric energy consumption. Besides, energy like natural gas is dissipated so severely that the utilization ratio of associated gas is less than 30%. This is obtained by analyzing energy distribution of system. For the seriously power-wasting problems in gathering system, energy saving technologies of small power pump replacing large power pump, intermittent pipelining oil by liquid level automatically controlled and double speed adjustment based on frequency control apply to the effective utilization of electric energy, which using oil pumps load rate as energy evaluation criterion. Applying technologies of helical down hole oil-gas separation and oil-gas airtight gathering to recover associated gas effectively gives conspicuous energy saving effect.

The oil–gas separation characteristics of ceramic/Teflon AF2400 composite membrane

We studied how the transformer oil flow rate affected the permeation characteristics of transformer fault gases in the ceramic/Teflon-AF2400 composite membrane, and we compared the permeation characteristics of the gases in the dissolved state and the gas state. When the oil flow rate increased from 250 to 750mL/min, the equilibrium time of H2 and CO reduced by about 40% while that of C2 hydrocarbons had little change, which indicated that the gas diffusion in the oil somewhat affected the oil–gas separation. The C2 hydrocarbons first reached permeation equilibrium in the dissolve state, whereas H2 first reached permeation equilibrium in the gas state. The FT-IR results indicated that after immersion in the transformer oil, the Teflon AF2400 membrane absorbed some transformer oil that formed a structure similar to supported liquid membrane. The solubility of the gases in the oil determined their permeation characteristics during the transformer oil–gas separation.

Research on the Oil-Gas Permeability of Mixed Hollow Fiber Membrane Made by PTFE and PHFP

Power transformer on-line monitoring on dissolved gas in oil is one of the effective and technical means to achieve the transformer state detection and fault diagnosis, and oil-gas permeability is one of the core technologies to implement transformer on-line monitoring. The traditional methods of oil-gas separation such as vacuum method and mechanical oscillation method were unable to satisfy the requirements of transformer on-line monitoring; and the methods which were used commonly in recent years, like dynamic headspace separation, corrugated tube, carrier gas elution etc, have a high rate of gas-separation and have already been used in some on-line monitoring products. However, the problems still exist: easy formation of oil pollution, so the oil can not be recycled and the device structure is relatively complex. This paper based on the separation principle of polymer membrane, proposes mixed hollow fiber membrane made by polytetrafluoroethylene (PTFE) and polyhexafluoropropylene (PHFP), and designs an oil-gas separation test platform formed by the storage tank, oil-gas permeability tank, temperature controller and gas chromatographic analyzer etc, does laboratory research on the oil-gas permeability of the mixed hollow fiber membrane at different temperatures. The results show that, the permeability of the mixed hollow fiber membrane is obviously better than the commonly used single fluoride film or rubber film, seven fault gases H2, CO, CO2, CH4, C2H6, C2H4, and C2H2 can be separated efficiently form transformer oil within 24 hours. More to the point, the equilibrium time is short, the gas permeability is high and the test platform structure is simple, all of these advantages provide a strong guarantee for the development of on-line monitoring technology on dissolved gas in transformer oil.

Effect of Temperature on Oil-Gas Separation in Membrane Separation Based Transformer On-Line Monitoring

In the same conditions, the transformer on-line monitoring and off-line chromatographic analysis should be consistent, but the actual on-line monitoring is effected by the ambient temperature to make it is different from the off-line chromatographic measurement. this paper analyzes the theory of oil-gas separation, and develops a gas-oil separation test platform first, conducts an experiment about the changes of temperature based on the device, and then compares with the data of off-line measurement, gets the law of temperature affection on the oil-gas separation process, Finally gives the reason of influence of ambient temperature on oil-gas separation in on-line monitoring.

Application of Pressure Test System in Dispenser for Gasoline

In the dispenser for gasoline there exist three problems: excessive pressure caused by water hammer, inadequacy of oil-gas separation and cavitation. A pressure test system of the dispenser for gasoline is established by using pressure transducers and a digital signal acquisition system. Results show that the pressure test system can not only conduct real-time and reliable diagnosis of the dispenser pressure, but also provide guideline on its performance optimization.

Investigation of the oil—gas separation in a horizontal separator for oil-injected compressor units

This article presents an investigation of the separation process as well as the separation efficiency for a horizontal oil—gas separator, which is widely used in the oil-injected compressor units. The trajectories of oil droplets with different diameters in the separator were simulated by using the discrete phase model in combination with the gas flow model. The laser diffraction technique (Malvern) was applied to measure the oil concentration and thereby the separation efficiency. By varying the parameters such as the oil injection flowrate, compressor discharge pressure, and oil—gas mixture inlet velocity, the main factors influencing the separation efficiency were identified. The results indicate that the trajectories together with the residence time of the oil droplets in the separator vary significantly with the droplet sizes. The separation efficiency increases from 99.81 to 99.93 per cent as the oil injection flowrate rises from 567 to 1182 l/h. An optimal discharge pressure exists for the separation efficiency, and the highest separation efficiency was obtained at a discharge pressure of 0.65 MPa. The simulated minimum oil droplet that can be separated completely during the first step separation is ∼17 μ m, which has a good agreement with the measured data of 17.7–20.5 μ m.