The Design, Development and Performance of Indair and Mardair Flares

ABSTRACT To meet the increasingly stringent requirements of safety and environmental pollution control, high technology flare systems have become a necessary part of the process system. EP has carried out a research and development programme to produce a new generation of flaring equipment and related practices to satisfy these requirements. The INDAIR and MARDAIR flare systems developed from this research are now in operation on both onshore and offshore installations around the world. The use of these new systems has enabled economies to be made in mast heights and boom lengths together with substantial improvements in safety and environmental pollution control. INTRODUCTION Early in 1967, as part of a programme to explore new burner concepts, BP Research Centre concieved the idea of using the Coanda effect as a means of entraining air into the gas supply of premixed gas burners. Preliminary experiments on internal venturi pumps, with throat diameters of a few inches, having a radially inward facing slot at the base as shown in Figure I, proved to be encouraging. The principle of operation of the device is quite simple. A laminar jet of fuel gas emerges from the slot at sonic velocity creating a low pressure region on either side of the jet. The low pressure region between the gas jet and the venturi walls causes the gas to cling to the venturi and the low pressure region on the other side of the film causes entrainment of air which is augmented by the change of direction of the gas as it follows the venturi form. In this way up to twenty volumes of air can be entrained per volume of fuel gas. Thjs primary air entrainment forms a core of air which is accelerated through the centre of the venturi to the velocity of the gas, at the burner exit. The near stochiometric ratio achieved creates a compact, non-luminous flame when ignited. Success with the internal Coanda air entrainment burner led to experimental work on the topological inversion, a tulip form with a radially outward facing gas exit as shown in Figure 2. The results obtained were similar to the venturi type burner, but the device had the obvious advantage of lending itself to scaling up within conventional manufacturing processes. With increasing safety and environmental pressures and the commencement of deep water exploration and production it was becoming increasingly apparent that a new approach to gas flaring and disposal systems was required. In BP's case the problem became particularly pressing with the discovery of oil in the North Sea Forties Field. This led the BP research team to concentrate its efforts on the development of new, high performance and high capacity gas flares to meet the new requirements. INDAIR FLARE DEVELOPMENT The first major flaring problem tackled by the research team arose on Das Island in the Southern Persian Gulf. This tiny island serves as a gathering centre for two large offshore reservoirs some distance away at Urn Shaif and Zakum.