Cryogenic Refrigerant Phase-Change Loop for Stable LNG Liquefaction
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Solution Overview
Problem
The process of liquefying natural gas using a refrigerant fluid with a change of phase is sensitive to variations in the composition of the gas, leading to inefficiencies due to the loss of lighter components and increased energy consumption as the refrigerant mixture composition changes, resulting in a rise in the lowest temperature that can be reached during evaporation.
Innovation Solution
A process that involves a cryogenic heat exchanger where a stream of natural gas flows in indirect contact with a refrigerant fluid mixture, which is expanded and reliquefied, with a phase separation and partial condensation in a condenser, followed by pre-cooling in a desuperheater to enhance heat exchange and condensation efficiency, reducing energy consumption by maintaining a stable refrigerant composition.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If a refrigerant fluid with change of phase is used for liquefying natural gas, then the liquefaction capacity is increased, but the composition stability of the refrigerant deteriorates due to loss of lighter components
Solution Approach 1:
The patent recovers lighter components that would otherwise be lost during the liquefaction process. A portion of the refrigerant fluid is diverted to a recovery system where lighter components are separated and returned to the refrigerant mixture, maintaining composition stability while preserving high liquefaction capacity
Solution Approach 2:
The patent implements a feedback mechanism where the composition of the refrigerant fluid is continuously monitored and adjusted. When lighter components are lost, the system automatically compensates by adjusting the refrigerant mixture composition, ensuring stable operation throughout the liquefaction process
2Temperature
If the refrigerant mixture composition changes due to component loss, then the lowest temperature reachable during evaporation increases, but the energy consumption increases
Solution Approach 1:
The patent actively manages the composition parameters of the refrigerant fluid to maintain optimal temperature characteristics. By adjusting the ratio of lighter to heavier components in the refrigerant mixture, the system maintains the lowest evaporation temperature while improving energy efficiency
Solution Approach 2:
By recovering lighter components that would otherwise be discarded, the patent prevents the refrigerant mixture from becoming too heavy, thereby maintaining low evaporation temperatures and reducing the energy required for the liquefaction process
3Use of energy by moving object
If a phase change process is used with refrigerant fluid, then the heat exchange efficiency is improved, but the complexity of the installation increases due to additional equipment
Solution Approach 1:
The patent combines multiple functions into integrated equipment. The phase separation unit is integrated with the refrigerant circulation system, and the composition adjustment mechanism is incorporated into the existing heat exchanger arrangement, reducing overall installation complexity while maintaining high heat exchange efficiency
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
This approach improves the efficiency of the liquefaction process by maintaining a stable refrigerant composition, reducing energy consumption, and enhancing heat exchange, thereby improving the overall efficiency of the liquefaction process.
Implementation Method 1
A first stream of first refrigerant fluid enters a first heat exchanger in a liquid state, passes through the heat exchanger in a co-current with a stream of natural gas and leaves it in the liquid state, said first stream of first refrigerant fluid in the liquid state being expanded in a first expander at the cold end of said first heat exchanger to the gaseous state
Implementation Method 2
said first stream of first refrigerant fluid in the liquid state being expanded in a first expander at the cold end of said first heat exchanger to the gaseous state
Implementation Method 3
a stream of natural gas flows in indirect contact with a refrigerant fluid mixture, which is expanded and reliquefied, with a phase separation and partial condensation in a condenser, followed by pre-cooling in a desuperheater to enhance heat exchange and condensation efficiency
Implementation Method 4
followed by pre-cooling in a desuperheater to enhance heat exchange and condensation efficiency
Data Source
AI summary
Process for liquefying natural gas in a cryogenic heat exchanger by flowing in indirect contact with refrigerant fluid entering heat exchanger at a first inlet at temperature T0 and pressure P1, and flowing through the exchanger as co-current with the natural gas stream, leaving the heat exchanger in the liquid state, then being expanded at the cold end of the exchanger to return to gaseous state at a pressure P′1 P1 and temperature T1 T0, before leaving the hot end of exchanger by outlet orifice in gaseous state T0. The fluid is then reliquefied to the inlet of the exchanger via compression followed by partial condensation and phase separation, a first liquid phase taken to the first inlet, a first gaseous portion compressed by a second compressor and cooled in desuperheater by contact with portion of the first liquid phase, prior to condensing in a second condenser.