Geometric design optimization of a prototype axial gas-liquid cyclonic separator

Abstract

Oil and gas industry faces new challenges these days: new off-shore fields are located in harsher environments, at longer distances from shore, in deeper waters, demanding more compact and efficient process facilities, to optimize investment costs and then, to guarantee the economic feasibility of these new projects. On the other hand, brown fields with decaying production experience significant changing process conditions which usually impose constrains in existing facilities. The bottle-necking of these facilities requires process improvements to increase their capacity and efficiency, minimizing at the same time any production deferment which could translates into unwanted higher operational costs. Usually, in both cases there are severe space limitations to deploy solutions, demanding these solutions to become more and more compact. PDVSA-Intevep has identified the need for a compact, high efficiency, and high capacity separation technology to address potential gas scrubbing problems in both green and brown fields, and started the development of an axial gas liquid cyclone as an answer to these needs. The separator consists of a flow conditioning section, a swirl generator section, and a segregating section with a discharge for gas and liquid phases in the outlet. An extensive planning, design, construction, and further experimental validation process of a prototype was conducted in the multiphase flow loop facilities of PDVSA-Intevep to demonstrate the axial cyclone concept. As a result of the experimental validation, several aspects of geometrical design were identified to be susceptible to improvements in order to achieve target separation efficiency. The geometric variables identified and addressed in order to improve the performance of this equipment are: incorporating a pre-separation chamber to remove segregated flow incoming to the device, a static mixer to homogenize the gas liquid mixture incoming to the swirl generator, improvement of swirl generator configuration for constructability purposes, improvement of the liquid annular outlet, gas recycle, and outlet gas flow conditioner configurations. The new design is the result of a comprehensive process of revisiting and evaluating the state-of-the-art of axial separation technologies, incorporating lessons learned during the concept demonstration tests and mechanistic modelling of the prototype. Design was conducted considering the operating envelope of the multiphase flow loop of PDVSA-Intevep, to carry out an experimental performance assessment of the incorporated improvements.