Hydrocyclones in Large-Scale Marine Oil Spill Cleanup

Abstract

ABSTRACT Depending on sea and weather conditions commercial oilspill recovery skimmers often recover a fluid stream which comprises 10% by volume oil and 90% unwanted seawater. Tests have recently been carried out to assess the technical suitability of a liquid-liquid hydrocyclone system in oilspill clean-up applications. These tests comprised an onshore oilspill simulation trial followed by participation in an offshore oilspill recovery exercise. The work indicated that a two stage, pump fed hydrocyclone system is capable of removing the majority of the recovered water, and deoiling this to acceptable levels of oil-in-water prior to discharge to sea. INTRODUCTION It is widely accepted that two key factors in handling large scale marine oilspill situations are rapid response and effective oil- water separation at the spill location. The latter allowing increased availability of on-site storage capacity, by ship-board separation and clean-up of free and to some extent emulsified water. Storage capacity is then left for relatively dry oil. When it is considered that high volume oilspill recovery devices such as pumps and weir systems may collect up to 90% by volume, free water with the oil, the benefts of separating and cleaning this volume of water on location, in terms of increased availability of storage capacity and time on-station are significant, and are illustrated in Figure 1. Liquid-liquid hydrocyclones have previously been proposed for such applications (reti), however this work concentrated on the emulsion breaking aspect and not on high volume water disposal. The objective of this work was to design and test a liquid-liquid hydrocyclone system which would effectively:De-oil free-water, which drops out of the recovered fluid in the ships storage, to an acceptable level to discharge to sea;Resolve the oil-water emulsion into wet oil and free water components, releasing more free water and further increasingstorage availability A test program was jointly sponsored by Kvaerner Process Systems A/S (KPS) and Conoco Specialty Products Inc. (CSPI). Two sets of trials have been carried out to assess the technical feasibility of VORTOIL. Hydrocyclone Technology in oilspill clean-up applicationsOnshore Oilspill Simulation Trial, Statens Forurensnings tilsyn, (SFT, State ollution Control Authority) Shorebase, Horten, Norway. 21 30 August, 1990.Offshore Oilspill Recovery Exercise, organized by Norsk Oljevernforening (NOFO, Norwegian Clean Seas Association for Operating Companies), Ula Field sector, Norwegian North Sea. 25-27 September, 1990. HYDROCYCLONE PRINCIPLE OF OPERATION The liquid-liquid hydrocyclone technology is based on patents derived from work at Southampton University, U.K, in the late seventies and early eighties, and enhanced by Conoco Specialty Products Inc., specifically to deal with oilspill type mixtures. Figure 2 shows the basic geometry and flow pattern of a single liquid-liquid hydrocyclone of the type already commonly used to de-oil produced water on offshore production facilities. Driven under pressure, the oil-water mixture enters the hydrocyclone where the flow is directed into a high velocity helical flow pattern by the geometry of the involute inlet. The heavier water phase migrates to the wall of the fine tapered section displacing the lighter oil phase to form a central low pressure core. The outer, water vortex passes down the length of the fine tapered section into the cylindrical tail section, exiting in the clean or downstream outlet.