The Molecular Gate adsorption process uses pressure swing adsorption (PSA) to remove nitrogen and carbon dioxide impurities from natural gas while using adsorbents with high selectivity between methane and these impurities. Two systems feeding smaller scale LNG plants are now operating where the methane rich feed is dehydrated and carbon dioxide is removed to 50 ppm or less. The Molecular Gate technology in LNG pretreatment is competitive with TSA based systems for lower carbon dioxide feed levels (such as for pipeline feed based peak shaver plants) and offers cost advantages and simplified operations as compared with amine plus TSA treatment for higher carbon dioxide concentrations. The technology removes water to <1 ppm and carbon dioxide to <50 ppm from any carbon dioxide feed level, with the treatment of carbon dioxide levels of up to 40% having been demonstrated. The Molecular Gate technology is also widely used to remove nitrogen from natural gas and in this application any carbon dioxide in the feed is automatically co-removed to less than 50 ppm. This paper provides an overview of the technology, the basis of the operating plants and outlines the application of the technology to feed streams over a range of carbon dioxide concentrations.
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