Gravitational and Centrifugal Oil-Water Separators with Plate Pack Internals

摘要

After some stages of treatment, most production water and other oily waste wateris discharged into the sea or onto other surface water. To protect the environment, the total amount of oil discharged must be kept to a minimum. Legislation with regard to the discharge of oil into the sea is being pursued in an international context. One of these is the Paris Convention, covering regulations for discharges from both offshore and onshore operations in and around the North Sea; a limit of 40 ppm monthly average has been agreed. Concerning gravity and centrifugal separators, theoretical studies have been carried out with respect to oil-droplet shape, forces acting on oil droplets and interactions of oil droplets with oil-water interfaces. For these types of separators, oil-droplet diameters within the critical range may be assumed to be rigid spheres; Stokes' law is valid. A generally applicable separation efficiency function has been derived analytically, which is valid for gravity separators as well as centrifuges. Computer simulations and laboratory experiments support the predictions of this function. Gravity plate separators are among the most frequently applied separator types in the oil-industry. The gravity plate separator is relatively cheap compared to other types of separators, but it is heavy and bulky and cannot always reach the target effluent oil concentration of 40 ppm. The centrifuge is one of the best separators. It can meet the Paris Convention requirements and gives good performance in relation to required deck space and weight. The main disadvantage of the centrifuge is its high cost.