HIGH PRESSURE GAS SWEETENING WITH AMINES FOR REDUCING CO_2 EMISSIONS

摘要

Natural gas sweetening is currently needed when the CO_2 content of the well stream is too high for meeting the customer contract specifications or transport requirements. But in combination with geological storage, it is also a measure for reducing the global CO_2 emissions. The aim of this article is to present the recent developments on natural gas sweetening with amine solutions for reducing CO_2 emissions. During the last five years, an experimental and modelling effort has been done to better understand and predict the CO_2 capture capacity of alkanolamines at high pressures. First, data of the equilibrium conditions were measured experimentally with real natural gas at the appropriate pressures and temperatures. Next, these data were used in combination with irreversible thermodynamics and advanced activity models to establish a model of the plant. Finally, the model was used to give better insight in the CO_2 capture plant on the Statoil operated gas platform Sleipner in the North Sea. Most importantly, it was experimentally observed that pressure has a significant and non-linear effect on the absorption capacity of the amines. The absorption capacity decreases with increasing pressure at constant CO_2 partial pressure or mole fraction. This is a non-desirable property, and can lead to lack of driving force for CO_2 capture in the absorber column. Moreover, mass and heat transfer behaviour and the effects of several additives to the amine solution were investigated experimentally with real natural gas at the appropriate pressures and temperatures.rnAt Sleipner Statoil uses this technology already since 1996. The Statoil operated LNG project Snohvit in Northern Norway and the BP-Sonatrach-Statoil operated gas field In Salah in Algeria will follow soon. Until now, all CO_2 is stored in an aquifer. But in the case oil and CO_2 rich natural gas fields are close together, the captured CO_2 could be used for Increased Oil Recovery (IOR). Concluding, natural gas sweetening is a first global application of capture & storage technology, and a promising technology for further reducing emissions of greenhouse gases in the near future.