EXERGY-BASED INVESTIGATION OF A COAL-FIRED ALLAM CYCLE

¹ Technical University of Berlin, Institute for Energy Engineering, Marchstr. 18, 10587 Berlin, Germany
² Technical University of Berlin, Institute for Energy Engineering, Marchstr. 18, 10587 Berlin, Germany

E-mail: Jing.luo@campus.tu-berlin.de; emelogu.ogechi@gmail.com; tetyana.morozyuk@tu-berlin.de; tsatsaronis@mailbox.tu-berlin.de

Abstract

Allam cycle is a novel cycle that capitalizes on the unique thermodynamic properties of supercritical CO₂ and the advantages of oxy-combustion for power generation. It is a high-pressure supercritical carbon dioxide cycle designed to combust fossil fuels such as natural gas or syngas (from coal gasification systems) with complete CO₂ separation at a high-efficiency and zero atmospheric emissions. This semi-closed cycle produces sequestration-ready/pipeline quality CO₂ by-product, and thus eliminates the need for additional CO₂-capture system. The Coal-fueled Allam cycle is targeted to deliver between 51-52% net efficiency (lower heating value) for coal gasification. In this study, the expected energetic efficiency is verified by simulating the system in Ebsilon professional software and the result showed that the net efficiency of the simulated coal-fired plant is 30.7%, which is significantly lower than the targeted value. The lower efficiency maybe as a result of the missing heat integration in the system, the high power demand of the oxidant compressor and CO₂ compressors. And an exergy analysis based on published cycle data is employed, to investigate the cycle performance, identify the sources of the cycle’s thermodynamic inefficiencies at the component level; a sensitivity analysis is also performed to study the effects of selected thermodynamic parameters on the overall performance of the coal-fired Allam cycle.