Identification and Quantification of CO2 Solidification in Cryogenic CO2 Capture from Natural Gas

Abstract

The composition of natural gas strongly depends on the geological conditions and depth of the gas well. Presently, CO2 content in the discovered natural gas reservoirs is up to 90%. Prior to customer use, the amount of CO2 needs to be reduced. Cryogenic CO2 capture is one of the emerging technology for CO2 capture from natural gas. Comprehensive knowledge of vapor-liquid, vapor-solid, and solid-liquid equilibria for the gaseous mixture is required for designing cryogenic separation processes for CO2 capture from its gaseous mixtures. No thermodynamic phase data is available for the highest CO2 content N.G mixture. The present work is an effort to generate the thermodynamic data for CO2 capture at low temperatures. CO2 solid phase identification and quantification need to be studied for the CO2-CH4 binary mixture. In this work, four samples of natural gas having CO2 content 40%, 60%, 75% and 90% were selected for simulation through Aspen HYSYS. Pressure-temperature data and temperature-composition data for the binary mixtures were predicted using PR EoS for CO2 phase identification and quantification respectively. Simulation for temperature- composition phase envelope was carried out at different pressures i.e. 10, 20, 30, and 40 bar. The operating region selected from the P-T phase envelop was from 1 to 40 bars. From the temperature composition graphs, it was concluded that temperature for the maximum CO2 capture in S-V region at 10, 20, 30, and 40 bar is -95, -90, -75, and -70 °C respectively.