Cascade LNG Refrigeration with Added Cooling Levels
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Solution Overview
Problem
Current natural gas liquefaction systems face challenges in achieving high thermodynamic efficiency while minimizing capital costs, particularly in the ethylene and methane cooling systems, where additional refrigeration capacity often results in increased costs without proportional returns.
Innovation Solution
The implementation of additional refrigeration levels in the heat exchanging economizers of the ethylene and methane refrigeration cycles generates multiple distinct refrigerant streams for indirect heat exchange, enhancing cooling efficiency with minimal additional equipment and capital expenditure.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Loss of energy
If additional refrigeration capacity is added to ethylene and methane cooling systems, then thermodynamic efficiency is improved, but capital cost increases
Solution Approach 1:
The refrigeration cycles are divided into multiple distinct cooling stages (first, second, third, and fourth cooling stages) with different refrigerants and temperature levels. Each stage handles a specific temperature range, allowing optimized heat exchange at each level without requiring a single complex high-capacity system, thus improving thermodynamic efficiency while controlling capital costs.
Solution Approach 2:
The patent introduces multiple refrigeration levels (temperature dimensions) by adding intermediate cooling stages between the ethylene and methane cycles. This creates a multi-dimensional temperature gradient structure with distinct warming and cooling passes at different temperature levels, enhancing thermodynamic efficiency through better heat exchange gradients without proportionally increasing capital investment.
2Productivity
If multiple distinct refrigerant streams are generated through additional refrigeration levels, then cooling efficiency is enhanced, but system complexity increases
Solution Approach 1:
The system generates multiple distinct refrigerant streams (first, second, third, and fourth refrigerant streams) from sequential flashing and compression stages. Each stream serves a specific cooling stage with optimized temperature and pressure characteristics, enabling efficient multi-level heat exchange while maintaining manageable system complexity through modular stage design.
Solution Approach 2:
The economizer serves multiple functions simultaneously: it acts as a heat exchange device, a refrigerant generation system, and a temperature gradient management component. The same economizer structure handles multiple refrigerant streams at different temperature levels, performing cooling, heating, and temperature regulation functions without requiring separate dedicated equipment for each function.
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 thermodynamic efficiency in natural gas liquefaction processes by reducing thermodynamic irreversibilities and capital costs, allowing for more efficient cooling with reduced capital investment, thereby optimizing the liquefaction of natural gas.
Implementation Method 1
The heat exchanging economizer facilitates indirect heat exchange between the predominantly methane stream and each of said four distinct refrigerant streams
Implementation Method 2
indirect heat exchange with at least a portion of each of the distinct refrigerant streams
Implementation Method 3
generating at least four distinct refrigerant streams from a common first refrigerant stream
Implementation Method 4
cooling at least a portion of the predominantly methane stream via indirect heat exchange
Data Source
AI summary
Cascade-type natural gas liquefaction methods and apparatus are provided, having enhanced thermodynamic efficiencies, through the use of added refrigeration levels in one or both of the ethylene and methane refrigeration systems thereof.