(106b) Novel Cryogenic CO2 Removal- Operating Conditions and Economic Analysis

Authors: 
Fazlollahi, F., Brigham Young University
Natural Gas (NG) pretreatment systems have been simulated to remove more than 99% of the CO2 from NG. Steady-state simulations with Aspen PlusTM illustrate the effects of different parameters on CO2 capture percentage. Vapor mole fractions of CO2 and methane also have been investigated by changing the pressure at constant temperature. Increasing pressure increases CO2 capture and hence methane mole fraction in the vapor. Consequently, mole fraction of CO2 in vapor decreases. As pressure increases, the methane in the vapor also condenses, creating more liquid in which solid CO2 can dissolve. Increasing methane increases both CO2 and C1 in the vapor stream and decreases the CO2 capture percentage. Increasing ethane and propane increases both CO2 and C1 in the vapor and decreases the CO2 capture percentage. An experimental bench-scale apparatus verified the simulation results. Exergy loss and heat exchange efficiency have been calculated and equipment sizes and cost estimates are complete. The results confirm the low exergy losses of 39.6 kWh/ kg treated NG for simulation and 44.8 kWh/ kg treated NG for bench-scale apparatus. High heat exchanger efficiency of +90% has been achieved. High pressure and low methane in NG composition results in high CO2 capture, though the capture efficiency reaches a maximum at intermediate pressure.