Evaluating the influence of H2O phase state on the performance of LNG oxy-fuel combustion power plant: Exergy and exergoeconomic analyses

• Published in: Applied thermal engineering Vol. 204; p. 118002
• Main Authors: Cai, Lei, Fu, Yidan, Cheng, Zeyang, Tan, Liping, Guan, Yanwen, Liu, Wenbin
• Format: Journal Article
• Language: English
• Published: Oxford Elsevier Ltd 05.03.2022; Elsevier BV
• Subjects: Carbon sequestration; Combustion temperature; Destruction; Economy; Exergoeconomic analysis; Exergy; Exergy analysis; Feasibility; Fuel combustion; Fuel systems; H2O phase state; Liquefied natural gas; LNG oxy-fuel combustion; Oxy-fuel; Phase transitions; Power plants; Economy; Exergy analysis; H2O phase state; Exergoeconomic analysis; LNG oxy-fuel combustion
• ISSN: 1359-4311; 1873-5606
• DOI: 10.1016/j.applthermaleng.2021.118002

•Exergy and exergoeconomic analyses are performed to LNG oxy-fuel combustion system.•Effect of two different phase states of H2O on system performance is given in detail.•Over 12% and 8% of exergy destruction in O2/water and O2/steam system can be avoided.•Avoidable total cost rate in O2/water and O2/steam systems achieve 53.36% and 33.61%.•Water is the better phase of diluent H2O concerning system exergy efficiency and economy. Oxy-fuel combustion with H2O as diluent is regarded as one of the most promising technologies to realize the carbon capture process in power plants. The phase state of H2O has a significant influence on system performance. In this paper, a novel oxy-fuel combustion system with the utilization of liquefied natural gas (LNG) cold energy is proposed. The effect of H2O phase states for improving potential and economy of the system is quantified using the exergy and exergoeconomic analysis methods. Results show that an O2/water system operates better than an O2/steam system, achieving an overall exergy efficiency of 36.35%, which is 4.7% higher than that of the latter. In the O2/water system, 11.99% of the exergy destruction can be avoided; this is, considerably higher than the 8.79% avoidable exergy destruction in the O2/steam system. In terms of economic feasibility, the total investment in the O2/water system is 1.86×105$/h, which is distinctly lower than the 3.47×105$/h investment in the O2/steam system. Moreover, the avoidable total cost rate in the O2/water system exceeds 53.36%, which is significantly higher than the 33.61% proportion in the O2/steam system. These results reveal that water is more suitable than steam for moderating the combustion temperature in oxy-fuel systems in terms of economic feasibility and exergy efficiency. This study is anticipated to have a positive influence on the global transition to a low-carbon future.