Recently, the rotational particle separator (RPS) was introduced as a new technique for separating solid and/or liquid particles of 0.1 lm and larger from gases. In this patented technique the principles of centrifugation are exploited to enhance separation of small-sized phases and particulate matter of density different from the carrier fluid. Practical designs of the RPS available in the market include equipment for purifying gases of industrial processes and portable air cleaners for domestic appliances. New developments are made in the area of the offshore industry. It concerns the separation of oil droplets from water and the separation of condensate, oil, and sand from natural gas. A particular feature of both designs is that the filter element is freely mounted in bearings and rotates, without the need of a motor, by introducing a swirl in the fluid flowing towards the filter element. The design is particularly suited for operation under high pressures as the rotating filter element is fully contained within a cylindrical pipe. The shaft does not pin through the external wall, so no sealing is required. Based on known RPS design principles and fluid flow relations an oil-water separator is designed and tested.

A novel gas separation process makes use of a rotating phase separator to separate micron-sized droplets from a gas stream. Based on an industrial scale design, a water/air separator is constructed and tested. The first experiment concerns the drainage of large fractions of separated liquid. During operation, drainage is observed via windows and a descriptive model is formulated. Because of the major influence on overall separation efficiency, liquid drainage is a key issue in the separator design. The second experiment comprises a droplet collection efficiency measurement using micron-sized droplets dispersed within the airstream. The separation efficiency of fine droplet removal is measured. This is an important factor in reducing capital costs.

A review is given of separation methods based on centrifugation. Attention is focused on separation of mixtures of gases and droplets. More particularly we consider: the method of gas centrifuges or ultra‐centrifuges to separate gases of different molecular weight, and centrifugal separators to separate droplets from gases. Elementary physical principles are used to formulate basic equations. From here on, rules are derived for separation performance, energy consumption and size of the installations. Status of technology of each of the methods is illustrated by presenting actual cases of application.

The rotational particle separator (RPS) is a compact device capable of separating micron-sized droplets from gases by centrifugation. Combined with expansion cooling in a turbine at semi-cryogenic temperatures, it provides the opportunity to remove contaminants like CO 2 and H 2 S from natural gas. Potential advantages of this technique are minimum energy consumption and compactness. To demonstrate its potential, an industrial scale RPS prototype is designed and constructed. Experiments are performed to check its overall performance. Both the hydrodynamic performance and the separation efficiency are satisfactory and correspond to theoretical predictions.