Dynamic column breakthrough measurements for increasing LNG production efficiency with cryogenic pressure swing adsorption

Abstract

The use of natural gas as a primary energy source is rapidly increasing on a global scale. To economically transport natural gas over long distances and satisfy this increase in demand, efficient production of liquefied natural gas (LNG) is required. Prior to the liquefaction of natural gas to produce LNG, it is highly desirable to remove N2 and CO2 impurities from the reservoir feed gas. Typically, CO2 is removed using a water-based amine solution. The regeneration of this amine solution is both energy intensive and costly. Furthermore, the amine solutions used are undesirable from health and environmental standpoints. Nitrogen is generally not removed prior to the liquefaction and must be separated from the end-flash vapor produced with the LNG. Conventionally this requires the construction of distillation towers operating at cryogenic conditions. In the environment of a cryogenic gas plant, adsorption-based processes for separating gases have several natural advantages over other methods. However, very little work has been done studying the efficiency of adsorption processes at the pressures and temperatures found in LNG plants. We have constructed a dynamic column breakthrough apparatus capable of measuring equilibrium adsorption and kinetics of adsorption at temperatures between 190 and 298 K and pressures to 1 MPa. This system was used to study the adsorption behaviour of N2, CO2 and CH4 on carbon molecular sieves and zeolites. This presentation will describe the measurement results and the challenges that were overcome as well as future plans to construct a larger scale apparatus.