Optimization of the Kalina cycle system 34 (KCS34) based on the addition of a second vapor-liquid separator

Vapor-liquid separator plays a critical role in the Kalina cycle system, particularly due to the zeotropic properties of ammonia-water mixture. Proper secondary vapor-liquid separation may further utilize the above characteristic. This paper proposes three restructured systems with the addition of a second separator for the Kalina Cycle System 34 (KCS34) and compares them with the original system. The results show that both the restructured system of type A, in which the second separator is placed upstream of Regenerator-1 and connected to the original separator via a throttle valve, and the restructured system of type B, in which the second separator is positioned before Regenerator-2 and connected to the original absorber, are superior to the original system, and the type B is even better. The restructured system of type C, in which the second separator is placed after Regenerator-2, only outperforms the original system at low intermediate pressures. Placing the second separator at the front end of Regenerator-2 has better thermodynamic performance compared to placing it at the back end. Placement at the front end of Regenerator-2 is preferred over placement at the front end of Regenerator-1. At an evaporation pressure of 3 MPa, the highest thermal efficiencies of the restructured system of type A, B and C are 12.04 %, 12.65 %, and 11.76 %, respectively, and the highest exergy efficiencies are 59.56 %, 62.59 %, and 58.16 %, respectively.