Centrifugal separation for cleaning well gas streams : from concept to prototype

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In-line centrifugal separation of dispersed phases

A new device - the rotational particle separator (RPS) - is compared to the cyclone for the removal of ultrafine particles, such as cryogenically condensed contaminant droplets from natural gas. The comparison focusses on identifying for each configuration the smallest size of particle which has a 50% chance of being removed from the gas stream. Whereas a cyclone can only separate 1 m droplets at very low-throughputs on the order of 1 MMscfd, at the same energy consumption and device volume, the rotational particle separator removes droplets of that size at throughputs of 300 MMscfd. The advantage of the rotational particle separator, therefore, lies in its compact separation potential for full-scale industrial gas well throughputs

Separation of carbon dioxide and methane in continuous countercurrent gas centrifuges

The goal of this study is to determine the order of magnitude of the maximum achievable separation for decontaminating a natural gas well using a gas centrifuge. Previously established analytical approximations are not applicable for natural gas decontamination. Numerical simulations based on the batch case show that although the separative strength of the centrifuge is quite good, its throughput is very limited. Both enrichment and throughput are only a function of length and peripheral velocity. A centrifuge with a length of 5 m and a peripheral velocity of approximately 800 m/s, would have a throughput of 0,57 mol/s and a product flow of 0,17 mol/s. These numbers are calculated with the assumption that the centrifuge is refilled and spun up instantaneously. The results for the countercurrent centrifuge show how the production rate varies as a function of internal circulation, product-feed ratio, peripheral velocity and centrifuge length and radius. Under conditions similar to those of the batch case the production is approximately half compared to the batch case, i.e. 0,08 mol/s. Optimization can yield a higher production at the cost of lower enrichment. Considering the current natural gas prices and the low production rate of the centrifuge, it is certain that the gas centrifuge will not generate enough revenue to make up for the high investment costs

Gas centrifugation with wall condensation

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Novel centrifugal process removes gas contaminants

A new technique based on centrifugal separation can economically process gas from fieldscontaminated with large amounts of carbon dioxide (CO2) or hydrogen sulfide (H2S).The process could help mitigate expected shortages in global natural gas supply during thenext few decades in an environmentally responsible manner. Current energy-intensivemethods often cannot economically remove CO2 or H2S in existing or newly discovered gasfields if the gas contains more than 15% CO2 or H2S.Selective absorption in an aqueous solution is the standard technique for removing thesegaseous contaminants from methane. High contamination levels, however, requireunacceptable levels of energy consumption for purification. These existing technologiesrequire more energy than the energy in the purified gas.Absorption and membrane technologies are understood processes that offer no economicprospects for these fields

Particle image velocimetry measurements of a steam-driven confined turbulent water jet

In this paper experiments are reported on a condensing steam jet. Superheated steam is injected at the bottom centre of a cylindrical water vessel, resulting in a turbulent jet with Reynolds numbers varying between $7.9{\times}10^4$ and $18.1{\times}10.4$, depending on the bulk temperature of the water. Near the steam inlet, the flow is two-phase with rapidly condensing steam. Downstream of a development region the jet is essentially single-phase. Using particle image velocimetry in a vertical plane through the central axis, instantaneous velocity fields of the single-phase region have been measured at a rate of 15Hz. The velocity field in this region is found to be self-similar, i.e. the width of the jet, $r_{1/2}$, increases linearly with increasing distance to the virtual origin, and a Gaussian profile prevails if velocities and distances are properly scaled. The spreading rate is equal to the one usually found in single-phase jets, and temperature independent. The virtual origin of the jet is positioned at a temperature-dependent distance (3–7 nozzle diameters) upstream of the steam inlet, and this distance is shown to correlate with the length of the condensation region. The turbulence intensity is found to be similar to the intensities usually reported for single-phase jets, although full isotropy is only reached at a distance of 15 nozzle diameters from the nozzle. The jet exhibits a slow wobbling motion, which can be attributed to instability of the backflow resulting from the confinement. When the measurements are compensated for this wobble, a slightly smaller spreading rate is obtained, which indicates that unconditional averaging may conceal significant flow structuring

Turbulence production by a steam-driven jet in a water vessel

Direct steam injection is an efficient means of heating a volume of liquid. Usually the steam is injected via a nozzle, yielding a strong jet that condenses rapidly and transforms into a self-similar single phase jet. In the experiments reported in this paper, superheated steam is injected, centrally, at the bottom of a vertical, cylindrical water vessel. The resulting jet is turbulent (Re=7.9×104-18.1×104 with the length scale based on the width of the jet, r1/2, and the velocity scale based on the centerline velocity, U0). Using PIV in a vertical plane through the central axis, instantaneous velocity fields have been measured at a rate of 15 Hz. Near the inlet, the jet is mainly steam that rapidly condenses. Further downstream, the jet is essentially single phase, although some residual air is present as microscopically small bubbles. In the area directly downstream of the steam part, the ratio of r1/2 to the vessel radius R (32.5 cm) is about 1/14. The production of turbulent kinetic energy has been quantified for the main process conditions. Its dependencies on temperature, nozzle opening and inlet steam pressure have been determined. This production of energy is related to the stresses exerted on small particles in the mixture, and break-up of particles is discussed