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[en] The oxygen-methane diffusion flame taking place in a gas turbine reactor was investigated experimentally with emphasis on flame stability. The oxidizer is a mixture of O_2 and CO_2 and the oxy-combustion process was studied at different equivalence ratios ranging from Φ = 0.5 to 1.0 and different O_2/CO_2 mixture composition (100/0, 80/20, 60/40, 50/50, 40/60, 30/70 and 25/75). The flame blowout condition was achieved through the reduction of oxygen percentage in the oxidizer mixture. Measurements were obtained for the flue gas temperature and concentration as well as flame visualization. It was found that the flame is very stable at the equivalence ratio of 0.65. At this ratio, the flame blows out at an O_2/CO_2 blending ratio of 22/78 for the case of fuel flow rate of 6 L/min and at a blending ratio of 21/79 for the case of fuel flow rate of 9 L/min. Attempts for operating the burner with less than 21% O_2 were unsuccessful at all ranges of the operating parameters and resulted in unstable operation and blowout. Moreover, it was observed that the stabilization behavior did not change significantly with the variation of the fuel volume flow rate. It was also found that both flame and flue gas temperatures are reduced with the increase of the equivalence ratio. - Highlights: • Stability and characteristics of oxy-combustion diffusion flame were investigated. • The flame blowout conditions was determined. • Visualization of flame is carried out and the exhaust gas temperature is measured. • It was found that the most stable flame is at an equivalence ratio of 0.65. • Attempts for operating the burner with less than 21% O_2 were unsuccessful
[en] A second law analysis of a reverse osmosis desalination plant is carried out using reliable seawater exergy formulation instead of a common model in literature that represents seawater as an ideal mixture of liquid water and solid sodium chloride. The analysis is performed using reverse osmosis desalination plant data and compared with results previously published using the ideal mixture model. It is demonstrated that the previous model has serious shortcomings, particularly with regard to calculation of the seawater flow exergy, the minimum work of separation, and the second law efficiency. The most up-to-date thermodynamic properties of seawater, as needed to conduct an exergy analysis, are given as correlations in this paper. From this new analysis, it is found that the studied reverse osmosis desalination plant has very low second law efficiency (<2%) even when using the available energy recovery systems. Therefore, an energy recovery system is proposed using the (PRO) pressure retarded osmotic method. The proposed alternative design has a second law efficiency of 20%, and the input power is reduced by 38% relative to original reverse osmosis system. -- Highlights: ► A previously proposed model for the calculation of seawater flow exergy gives incorrect values. ► Reverse osmosis desalination plants have very low second law efficiency (<2%) even when using the available energy recovery systems. ► A PRO energy recovery device increases the RO plant’s second law efficiency to 20% and reduces the input power.