Efficient electrochemical refrigeration power plant using natural gas with ∼100% CO₂ capture

We propose an efficient Natural Gas (NG) based Solid Oxide Fuel Cell (SOFC) power plant equipped with ∼100% CO₂ capture. The power plant uses a unique refrigeration based process to capture and liquefy CO₂ from the SOFC exhaust. The capture of CO₂ is carried out via condensation and purification using two rectifying columns operating at different pressures. The uncondensed gas mixture, comprising of relatively high purity unconverted fuel, is recycled to the SOFC and found to boost the power generation of the SOFC by 22%, when compared to a stand alone SOFC. If Liquefied Natural Gas (LNG) is available at the plant gate, then the refrigeration available from its evaporation is used for CO₂ Capture and Liquefaction (CO₂CL). If NG is utilized, then a Mixed Refrigerant (MR) vapor compression cycle is utilized for CO₂CL. Alternatively, the necessary refrigeration can be supplied by evaporating the captured liquid CO₂ at a lower pressure, which is then compressed to supercritical pressures for pipeline transportation. From rigorous simulations, the power generation efficiency of the proposed processes is found to be 70-76% based on lower heating value (LHV). The benefit of the proposed processes is evident when the efficiency of 73% for a conventional SOFC-Gas turbine power plant without CO₂ capture is compared with an equivalent efficiency of 71.2% for the proposed process with CO₂CL.