Power recovery system using a rankine power cycle incorporating a two-phase liquid-vapor expander with electric generator
A power recovery system using the Rankine power cycle incorporating a two-phase liquid-vapor expander with an electric generator which further consists of a heat sink, a heat source, a working fluid to transport heat and pressure energy, a feed pump and a two-phase liquid-vapor expander for the working fluid mounted together with an electric generator on one rotating shaft, a first heat exchanger to transport heat from the working fluid to the heat sink, a second heat exchanger to transport heat from the heat source to the working fluid.
1. A method for power recovery using a two-phase fluid Rankine power cycle in an LNG regasification plant in which the working fluid is LNG, the method comprising the following steps:
containing the working fluid in a closed loop;
with work input, pressurizing incoming liquid, single phase working fluid from low pressure to high-pressure across a feed pump mounted on a rotating axial shaft;
heating and partially vaporizing the working fluid by passing it through induction generator commonly mounted on the rotating axial shaft, and then through a first heat exchanger where heat is transferred to the working fluid by sea water, the first heat exchanger heating the pressurized working fluid into higher vapor content;
expanding the pressurized and heated two-phase saturated working fluid from high-pressure to low-pressure across a two-phase liquid-vapor expander also commonly mounted on the rotating axial shaft, thereby driving the rotating axial shaft and induction generator and generating a work output; and
passing the expanded low pressure two-phase saturated working fluid from the two-phase liquid-vapor expander through a second heat exchanger such that the expanded low pressure two-phase saturated working fluid is cooled by single phase liquid LNG and condenses from its saturated liquid-vapor two-phase state back to a non-saturated liquid single phase state.