LNG Liquefaction System and Process
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Solution Overview
Problem
Current natural gas liquefaction processes face inefficiencies in achieving cryogenic temperatures and recycling refrigeration streams effectively, leading to suboptimal energy usage and product quality.
Innovation Solution
A method involving the mixing of clean and recycled gas streams, passing through a heat exchanger with refrigeration streams, and utilizing turbo-expanders and compressors to form and recycle refrigeration streams, achieving cryogenic temperatures and efficient liquefaction of natural gas.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If refrigeration streams are used to cool gas streams to cryogenic temperatures, then liquefaction efficiency is improved, but energy loss increases due to heat exchange requirements
Solution Approach 1:
The patent combines multiple refrigeration streams (first refrigeration stream from warm turbo-expander, second refrigeration stream from cold turbo-expander, and third refrigeration stream from slipstream) into a unified cooling system. These streams are merged to cool different portions of the natural gas feed stream simultaneously, achieving cryogenic temperatures more efficiently while recovering and utilizing the cooling capacity of each stream before compression, thereby reducing overall energy loss.
2Temperature
If multiple refrigeration streams are generated and recycled, then cryogenic temperature achievement is improved, but system complexity increases
Solution Approach 1:
The patent segments the refrigeration system into three distinct refrigeration streams, each serving a specific cooling function: the first refrigeration stream cools the natural gas feed stream to intermediate temperatures, the second refrigeration stream provides additional cooling to achieve lower temperatures, and the third refrigeration stream from the slipstream provides final cooling to reach cryogenic temperatures. This segmentation allows each stream to be optimized for its specific temperature range while maintaining overall system manageability.
Solution Approach 2:
The patent designs the refrigeration streams to serve multiple functions within the system. The same refrigeration streams that cool the natural gas feed stream are also used to pre-cool the compressed gas before it enters the next compression stage, and to cool the refrigeration streams themselves during compression. This multi-functionality reduces the need for separate cooling systems and simplifies the overall architecture despite the multiple streams.
3Manufacturing precision
If gas streams are split and processed through multiple paths, then liquefaction quality is improved, but process time increases
Solution Approach 1:
The patent implements preliminary cooling actions by passing the natural gas feed stream through the first refrigeration stream before main compression, and through the second refrigeration stream before final liquefaction. The slipstream is also pre-cooled before being combined with the main stream. These preliminary actions prepare the gas for subsequent processing stages, ensuring that each stage receives pre-conditioned gas, which improves liquefaction quality while minimizing additional process time through efficient sequential processing.
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 enhances the efficiency of natural gas liquefaction by effectively recycling refrigeration streams and achieving desired cryogenic temperatures, improving the quality and yield of liquefied natural gas while optimizing energy usage.
Implementation Method 1
passing the first stream and the second stream through a heat exchanger; wherein the heat exchanger cools the first stream to form a first liquefied stream by cross exchanging with one or more refrigeration streams
Implementation Method 2
passing the first split stream through a warm turbo-expander to form the warm expander refrigeration stream
Implementation Method 3
passing the second split stream through the heat exchanger and a cold turbo-expander to form a cooled split stream
Implementation Method 4
passing the cooled split stream through a cold separator to separate the cooled split stream into a second liquefied stream and the cold expander refrigeration stream
Implementation Method 5
compressing the secondary refrigeration return gas stream using a first compressor to form a compressed secondary refrigeration return gas stream
Data Source
AI summary
The present invention comprises systems and methods for natural gas liquefaction. In embodiments, the systems comprise a dual turbo-expander, methane-based refrigeration system that also uses a slip stream of LNG for additional cooling.