Ship Boil-Off Gas Reliquefaction Using Segmented Refrigerant Flows
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Existing boil-off gas reliquefaction systems in ships are inefficient in terms of power consumption and reliquefaction efficiency due to the reliance on a single refrigerant process, which limits the ability to completely utilize boil-off gas for reliquefaction.
Innovation Solution
A multistage compressor system with multiple heat exchangers is employed, where boil-off gas is compressed, cooled, and divided into two flows for further cooling and expansion, utilizing the gas itself as a refrigerant in a partial reliquefaction process to reduce the amount of gas used for reliquefaction and lower energy consumption.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If a single refrigerant process is used for boil-off gas reliquefaction, then the system structure is simple, but the reliquefaction efficiency is low and power consumption is high
Solution Approach 1:
The patent divides the refrigerant flow into multiple stages: a first refrigerant flow for initial cooling and a second refrigerant flow for further cooling. This segmentation allows each flow to perform its cooling function independently and efficiently, thereby improving overall reliquefaction efficiency without creating a single complex integrated system
Solution Approach 2:
The patent introduces a multi-dimensional approach by creating parallel refrigerant flow paths (first and second refrigerant flows) that operate simultaneously. This dimensional expansion from a single flow to multiple flows enables more efficient heat exchange while maintaining manageable system architecture through modular heat exchanger units
2Productivity
If more boil-off gas is used as refrigerant, then reliquefaction efficiency improves, but power consumption of the compressor increases
Solution Approach 1:
The patent segments the refrigerant gas into two separate flows, where only the necessary amount of gas is diverted for refrigeration purposes. The first refrigerant flow handles primary cooling while the second handles secondary cooling, allowing optimized gas distribution that improves reliquefaction efficiency without requiring excessive compressor power
Solution Approach 2:
The patent utilizes parameter changes in the refrigerant flows, including temperature and pressure variations across different heat exchangers. By optimizing these parameters for each refrigerant flow separately, the system achieves efficient reliquefaction with minimized compressor work requirements
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 reliquefaction efficiency while reducing power consumption by diversifying the refrigerant usage and optimizing the compression process, allowing for more efficient boil-off gas reliquefaction with lower energy expenditure.
Implementation Method 1
a multistage compressor including a plurality of compression cylinders to compress boil-off gas discharged from the storage tank
Implementation Method 2
a first heat exchanger cooling the fluid compressed by the multistage compressor by subjecting the fluid to heat exchange with the boil-off gas discharged from the storage tank
Implementation Method 3
a first decompressor expanding one (hereinafter referred to as 'flow a1') of two flows branching off of the fluid cooled by the first heat exchanger
Implementation Method 4
a third heat exchanger cooling the other flow (hereinafter referred to as 'flow a2') of the two flows by subjecting the flow a2 to heat exchange with the flow a1 expanded by the first decompressor to be used as a refrigerant
Implementation Method 5
a second decompressor expanding the flow a2 cooled by the third heat exchanger
Data Source
AI summary
A ship comprises: a tank; a multistage compressor for compressing a boil-off gas discharged from a storage tank and comprising a plurality of compression cylinders; a first heat exchanger for heat exchanging a fluid, which has been compressed by the multistage compressor, with the boil-off gas discharged from the storage tank and thus cooling the same; a first decompressing device for expanding a flow (“flow a1”) partially branched from the flow (“flow a”) that has been cooled by the first heat exchanger; a third heat exchanger for heat exchanging, by “flow a1” which has been expanded by the first decompressing device as a refrigerant, the remaining flow (“flow a2”) of “flow a” after excluding “flow a1” that has been branched and thus cooling the same; and a second decompressing device for expanding “flow a2” which has been cooled by the third heat exchanger.