Method and system for efficient nonsynchronous LNG production using large scale multi-shaft gas turbines
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Solution Overview
Problem
Current LNG production methods using single-shaft gas turbines require large electrical motors and variable frequency drives, leading to inefficiencies and increased costs, especially in large-scale operations, as they necessitate a fixed speed operation and additional power generation capacity, which is not optimal for maximizing LNG train capacities and reducing capital costs.
Innovation Solution
Implementing a multi-shaft gas turbine system that operates non-synchronously, eliminating the need for electrical motors and variable frequency drives by utilizing its inherent speed turndown range to start and adjust compressor operating points, thereby maximizing efficiency across multiple refrigeration compression strings without additional assistance.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If single-shaft gas turbines are used to drive refrigeration compressors in LNG production, then the system can operate with a fixed speed, but it requires large electrical motors and variable frequency drives, increasing device complexity and capital costs
Solution Approach 1:
The patent removes the electrical motor and variable frequency drive components from the system by using a multi-shaft gas turbine that directly drives the compressors. The turbine's inherent ability to operate at different speeds on different shafts eliminates the need for external speed control devices, thereby reducing device complexity while maintaining operational reliability.
Solution Approach 2:
The multi-shaft gas turbine serves its own speed control function internally through its design, with each shaft capable of operating at different speeds independently. This self-regulating capability eliminates the need for external variable frequency drives, allowing the system to maintain fixed speed operation where needed while providing flexibility where required, without adding external control complexity.
2Ease of operation
If single-shaft gas turbines operate at fixed speed, then the system is simpler to control, but it cannot maximize efficiency across multiple compression strings with different power requirements
Solution Approach 1:
The patent divides the gas turbine into multiple independent shafts, each capable of operating at different speeds. This segmentation allows each compression string to receive appropriate power at optimal speeds, maximizing overall system productivity while maintaining simpler control for each individual shaft compared to coordinating multiple motors and drives.
Solution Approach 2:
The multi-shaft gas turbine provides dynamic speed adjustment capabilities where each shaft can operate at different rotational speeds independently. This dynamic flexibility allows the system to optimize efficiency for each compression string's specific power requirements while maintaining operational simplicity, thereby increasing overall LNG train capacity without requiring complex external control systems.
3Productivity
If large scale LNG trains are developed with multiple compression strings, then the production capacity increases, but the capital cost and footprint increase proportionally
Solution Approach 1:
The patent combines multiple compression strings into a single integrated multi-shaft gas turbine system rather than using separate turbines for each string. This merging reduces the overall number of major equipment items, minimizes the facility footprint, and lowers capital costs while maintaining high production capacity through the turbine's ability to drive multiple compressors simultaneously at optimized speeds.
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 enables efficient large-scale LNG production with reduced capital and operational expenses, allowing for higher capacities (e.g., exceeding 7-8 MTA) while minimizing the number of components and footprint, and optimizing gas turbine power use through flexible speed control and power reallocation within the LNG train.
Implementation Method 1
uses its inherent speed turndown range to start the one or more refrigeration compressors from rest, bring the one or more refrigeration compressors up to an operating rotational speed
Implementation Method 2
adjust compressor operating points to maximize efficiency of the one or more refrigeration compressors
Data Source
AI summary
A drive system for liquefied natural gas (LNG) refrigeration compressors in a LNG liquefaction plant. Each of three refrigeration compression strings include refrigeration compressors and a multi-shaft gas turbine capable of non-synchronous operation. The multi-shaft gas turbine is operationally connected to the refrigeration compressors and is configured to drive the one or more refrigeration compressors. The multi-shaft gas turbine uses its inherent speed turndown range to start the one or more refrigeration compressors from rest, bring the one or more refrigeration compressors up to an operating rotational speed, and adjust compressor operating points to maximize efficiency of the one or more refrigeration compressors, without assistance from electrical motors with drive-through capability and variable frequency drives.