Novel High-Perfoming Single-Pressure Combined Cycle With CO₂ Capture

The European electric power industry has undergone considerable changes over the past two decades as a result of more stringent laws concerning environmental protection along with the deregulation and liberalization of the electric power market. However, the pressure to deliver solutions in regard to the issue of climate change has increased dramatically in the last few years and given the rise to the possibility that future natural gas-fired combined cycle (NGCC) plants will also be subject to CO₂ capture requirements. At the same time, the interest in combined cycles with their high efficiency, low capital costs and complexity has grown as a consequence of addressing new challenges posed by the need to operate according to market demand in order to be economically viable. Considering that these challenges will also be imposed on new natural gas-fired power plants in the foreseeable future, this study presents a new process concept for natural gas combined cycle power plants with CO₂ capture. The simulation tool IPSEpro is used to model a 400 MW single-pressure NGCC with post-combustion CO₂ capture, using an amine-based absorption process with Monoethanolamine. To improve the costs of capture the gas turbine, GE 109FB, is utilizing exhaust gas recirculation, thereby increasing the CO₂ content in the gas turbine working fluid to almost double that of conventional operating gas turbines. In addition, the concept advantageously uses approximately 20% less steam for solvent regeneration by utilizing preheated water extracted from HRSG. The further recovery of heat from exhaust gases for water preheating by use of an increased economizer flow results in an outlet stack temperature comparable to those achieved in combined cycle plants with multiple pressure levels. As a result, overall power plant efficiency as high as that achieved for a triple-pressure reheated NGCC with corresponding CO₂ removal facility is attained. The concept thus provides a more cost-efficient option to triple-pressure combined cycles since the number of heat exchangers, boilers, etc. is reduced considerably.