Comparative Study of Two Low CO2 Emission Cycle Options With Natural Gas Reforming

Abstract

Two power plant schemes with natural gas reforming and CO2 emission reduction were analyzed and discussed. The first one integrates natural gas reforming technology with an oxy-fuel combined power cycle (OXYF-REF), with water as the main work fluid. The reforming heat is obtained from the available turbine exhaust heat, and the produced syngas is used as fuel with oxygen as the oxidizer. The turbine working fluid can expand down to a vacuum, producing a high pressure ratio. The second system adopts pre-combustion decarbonization and a chemical absorption technology for CO2 removal (PCD-REF). The gas turbine is the conventional air based one with compressor intercooling. Supplementary combustion is adopted to elevate the turbine exhaust temperature and thus achieve a much higher methane conversion rate (∼95%). Both cycles involve internal heat recuperation from gas turbine exhausts, and particular attention has been put on the integration of heat recovery chain to reduce the related exergy destruction. The systems are simulated and compared in terms of both thermal efficiency and CO2 removal. The OXYF-REF cycle has shown better performance with higher levels of CO2 removal and energy efficiency of 52%. The PCD-REF cycle showed a thermal efficiency of 43% and CO2 specific emission of 55.5 g/kWh.