Two-Phase LNG Expander for Regasification Energy Recovery
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Solution Overview
Problem
Conventional LNG regasification processes are inefficient in recovering energy, as existing one-phase turbine and generator combinations are ineffective due to high pressure and mechanical turbulence, causing corrosion and damage from liquid droplets, and there is a lack of systems integrating the Rankine power cycle with LNG regasification using sea water as a heat source at lower temperatures.
Innovation Solution
A power recovery system utilizing a compact Rankine power cycle with a two-phase LNG expander and induction generator integrated on a single rotating shaft, which converts the work output difference into electrical energy, minimizing losses and leveraging sea water and other heat sources, while maintaining a closed loop to prevent fluid leakage and reduce axial thrust.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Loss of energy
If a one-phase turbine and generator combination is used for power recovery, then the system structure is simple, but the energy recovery efficiency is low and the equipment suffers corrosion and damage from liquid droplets
Solution Approach 1:
The patent changes the operational parameters by using a two-phase expander that can handle liquid-vapor mixtures instead of a one-phase turbine designed for vapor only. This allows the system to process LNG directly in two-phase state, improving energy recovery efficiency while avoiding the harmful effects of liquid droplets damaging turbine blades through specialized two-phase flow handling capabilities
Solution Approach 2:
The invention utilizes phase transitions by implementing a two-phase liquid-vapor expander that operates with LNG in both liquid and vapor states simultaneously. This approach captures energy from the phase change process itself, converting the thermodynamic potential of two-phase flow into mechanical work, thereby improving energy recovery efficiency while avoiding equipment damage through proper two-phase flow management
2Loss of energy
If a compact Rankine power cycle with two-phase expander and integrated generator is used, then energy recovery efficiency increases, but the device complexity increases
Solution Approach 1:
The patent merges the expander and generator into a single integrated unit where the expander shaft is directly coupled to the generator. This combination reduces the number of separate components and connections, simplifying the overall system structure while maintaining high energy recovery efficiency through direct energy conversion from the two-phase expansion process
Solution Approach 2:
The two-phase expander is designed to perform multiple functions: it expands the two-phase LNG flow to generate mechanical work, handles the two-phase fluid distribution, and directly drives the generator. This multi-functionality reduces the need for separate components, thereby reducing system complexity while improving energy recovery efficiency
3Stress or pressure
If high pressure is used to compress LNG in liquid state, then the send-out pressure is sufficient for pipeline delivery, but the pump size and energy consumption increase
Solution Approach 1:
The patent changes the compression approach by using a two-phase expander operating at lower pressures to achieve the required send-out pressure. Instead of using a large high-pressure pump, the system utilizes the expansion of two-phase LNG to generate the necessary pressure differential, thereby reducing pump energy consumption while maintaining sufficient send-out pressure for pipeline delivery
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
The system efficiently recovers input energy during LNG regasification, increasing thermodynamic efficiency, reducing equipment damage, and extending bearing life by minimizing axial thrust and fluid leakage, with the expander work output exceeding pump input, generating electrical energy from the recovered work difference.
Implementation Method 1
Power recovery system using a Rankine power cycle incorporating a two-phase liquid-vapor expander with electric generator
Implementation Method 2
two-phase expander generator that generates electrical energy during regasification
Implementation Method 3
The naturally stored 'heat' in sea water is a heat source for heating and vaporizing LNG
Data Source
AI summary
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.