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.
Highlights
Coal is regarded as one of the largest resources for power generation worldwide
We present the findings of the thermodynamic and exergetic analysis of the coal-fired Allam cycle which forms the bedrock for further discussions on the effects of important process parameters on cycle performance
The net efficiency of the coal-fired Allam cycle in this study is 30.7 %; the principal parasitic loads of the plant as shown in Table 5 below include: The Air Separation Unit, the CO2, syngas, and oxidant compressor
Summary
Coal is regarded as one of the largest resources for power generation worldwide. According to International Energy Agency (IEA), coal-fired power generation increased by approximately 3% in 2017 and in 2018, reaching a new peak above 10,000 TWh [1]. Over 30% of the global energy demand and over 40% of the electricity generated is derived from coal, owing to the fact that it is a secure and relatively low‐cost source of energy, and the resources are abundant and broadly distributed geographically [2]. With the significantly increasing demand in global energy, comes the challenge of increasing CO2 emissions, of which coal-fired power plants are major contributors. In a bid to reduce CO2 emissions from power generating plants, several solutions have been proposed and developed. The carbon capture and storage (CCS) is one of such Incorporation of this solution presents detrimental efficiency penalty and increased price of electricity due to the high cost of additional equipment. Novel technologies that generate electricity from coal with reduced CO2 emissions and high efficiency are being developed
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