Multi-Shaft LNG Compressor Drive Without Variable Frequency Drives
Find Innovative SolutionsGenerate Solutions
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 due to power imbalances and the need for multiple compression strings, which can be costly and environmentally impactful.
Innovation Solution
Implementing a system with multi-shaft gas turbines capable of non-synchronous operation to drive refrigeration compressors, eliminating the need for electrical motors and variable frequency drives by utilizing the turbines' inherent speed turndown range to start and optimize compressor efficiency, and configuring multiple compression strings to handle different refrigerants.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If single-shaft gas turbines are used to drive refrigeration compressors, then the system can operate, but it requires large electrical motors and variable frequency drives which increase capital costs and device complexity
Solution Approach 1:
The patent extracts and removes the electrical motor and variable frequency drive components from the compression string, replacing them with a gas turbine that directly drives the compressor through mechanical coupling. This eliminates the need for electrical starting equipment and speed control devices, thereby reducing capital costs and device complexity while maintaining operational capability.
Solution Approach 2:
The patent replaces the electrical-mechanical drive system (electrical motor + variable frequency drive + compressor) with a direct gas turbine-mechanical drive system. The gas turbine's rotating shaft is mechanically coupled to the compressor, substituting electrical control mechanisms with direct mechanical power transmission, which simplifies the system and reduces component count.
2Productivity
If multiple compression strings are installed to increase LNG production capacity, then production capacity increases, but capital cost and environmental footprint increase
Solution Approach 1:
The patent merges the functions of multiple compression strings into a single integrated compression string by using a gas turbine with enhanced output capacity. Instead of installing multiple separate compressor-train assemblies, the gas turbine provides sufficient power to drive all necessary compressors within one streamlined configuration, achieving the same production capacity with reduced capital cost and smaller environmental footprint.
Solution Approach 2:
The gas turbine serves multiple functions simultaneously: it provides the primary driving power for the compression string, enables flexible operation across varying load conditions, and allows for efficient operation at different production rates. This multi-functionality replaces the need for multiple specialized compression strings, reducing overall system complexity and cost.
3Use of energy by moving object
If single-shaft gas turbines with variable frequency drives are used, then compressor operating efficiency can be optimized, but the system requires electrical motors which increase operational expenses
Solution Approach 1:
The gas turbine operates continuously to provide mechanical power to the compressor through direct shaft coupling, eliminating energy conversion losses associated with electrical motors and variable frequency drives. The mechanical power transmission maintains continuous useful action from fuel combustion to compressor work, reducing energy losses and operational expenses while preserving the ability to optimize compressor operating efficiency through turbine control.
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 reduces capital costs, minimizes the number of components, and enhances efficiency by maximizing LNG production capacity while reducing the environmental footprint and operational expenses.
Implementation Method 1
a multi-shaft gas turbine capable of non-synchronous operation, the multi-shaft gas turbine being operationally connected to the one or more refrigeration compressors
Implementation Method 2
large scale multi-shaft gas turbines...uses its inherent speed turndown range to start the one or more refrigeration compressors from rest
Implementation Method 3
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
Implementation Method 4
first, second, and third refrigeration compression strings, each refrigeration compression string including one or more refrigeration compressors
Implementation Method 5
the multi-shaft gas turbine being operationally connected to the one or more refrigeration compressors and configured to drive 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.