System for processing liquefied gas on vessel
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Solution Overview
Problem
Conventional liquefied gas carriers face challenges in efficiently managing boil-off gas (BOG) due to continuous vaporization, leading to structural issues and inefficient fuel utilization, with existing reliquefaction methods being complex and energy-intensive.
Innovation Solution
A liquefied gas treatment system that compresses and liquefies BOG using a compressor and pump, then decompresses it using a heat exchanger and decompressing means, allowing for its reuse as fuel or reliquefaction without a separate refrigerant, thereby reducing BOG consumption and energy consumption.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a conventional reliquefaction apparatus using a separate refrigerant is used, then BOG can be reliquefied and returned to the cargo tank, but the system becomes complex and energy-intensive
Solution Approach 1:
The invention extracts and utilizes the cold energy already present in the cargo tank environment rather than introducing a separate refrigerant system. The BOG is cooled by the cold surroundings of the cargo tank itself, eliminating the need for complex external reliquefaction apparatus and separate refrigerants.
Solution Approach 2:
The cargo tank's cold environment serves itself by providing the cooling necessary for BOG reliquefaction. The system uses the inherent cold energy of the stored liquefied gas to cool and reliquefy the BOG, making the system self-sufficient and eliminating the need for additional energy-intensive refrigeration equipment.
2Reliability
If BOG is continuously discharged and burned, then cargo tank pressure is maintained, but fuel is wasted and operational costs increase
Solution Approach 1:
Instead of discarding BOG through combustion, the invention recovers it by reliquefying and returning it to the cargo tank. This prevents fuel waste while maintaining cargo tank pressure control, converting a loss process into a recovery process.
Solution Approach 2:
The invention changes the state parameter of BOG from gas to liquid through cooling, enabling it to be stored back in the cargo tank rather than being burned. This phase change allows the system to maintain pressure control without fuel consumption.
3Loss of energy
If thermal insulation of the cargo tank is improved, then BOG generation is reduced, but initial installation cost increases
Solution Approach 1:
The invention creates a secondary cooling path by using the cold energy already available in the cargo tank environment, rather than relying solely on improving the primary thermal insulation. This alternative approach achieves BOG reduction without requiring expensive insulation upgrades.
4Reliability
If a separate refrigerant system is installed for BOG reliquefaction, then BOG can be treated, but initial installation and operational costs increase
Solution Approach 1:
The cargo tank's cold environment serves multiple functions: storing liquefied gas and simultaneously providing the cooling necessary for BOG reliquefaction. This multi-functionality eliminates the need for separate refrigeration systems and reduces both installation and operational costs.
Solution Approach 2:
The invention merges the BOG treatment function with the existing cargo tank storage function. By utilizing the cargo tank's cold environment for both storage and cooling purposes, the system combines multiple functions into a single integrated solution, reducing overall system cost.
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
The system effectively utilizes all BOG as fuel, reduces BOG consumption, eliminates the need for energy-intensive reliquefaction apparatuses, and saves on initial installation and operational costs by avoiding the use of separate refrigerants.
Implementation Method 1
a compressor line configured to compress BOG generated in the cargo tank by a compressor
Implementation Method 2
a heat exchanger configured to liquefy at least a part of BOG, which is compressed by the compressor, by exchanging heat with BOG that is discharged from the cargo tank
Implementation Method 3
liquefy at least a part of BOG... by exchanging heat
Implementation Method 4
decompressing means configured to decompress the BOG liquefied by the heat exchanger
Data Source
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AI summary
Provided is a liquefied gas treatment system for a vessel, which includes a cargo tank storing liquefied natural gas (LNG), and an engine using the LNG as fuel. The liquefied gas treatment system includes: a compressor line configured to compress boil-off gas (BOG) generated in the cargo tank by a compressor and supply the compressed BOG to the engine as fuel; a high pressure pump line configured to compress the LNG stored in the cargo tank by a pump and supply the compressed LNG to the engine as fuel; and a heat exchanger configured to liquefy a part of BOG, which is compressed by the compressor, by exchanging heat with BOG that is discharged from the cargo tank and transferred to the compressor.