Multi-Circuit Gas Supply With Heat Treatment for Boil-Off Control
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Solution Overview
Problem
Ships using liquid-state gas for propulsion face high costs and vibrations due to expensive high-pressure compression devices, and existing methods to manage boil-off gas are inefficient.
Innovation Solution
A gas supply system with multiple circuits, heat exchangers, and a heat treatment branch that optimizes the use of vapor-state gas for condensation, reducing the need for high-pressure compression and improving energy efficiency.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Stress or pressure
If high-pressure compression devices are used to compress gas to 300 bar absolute for ME-GI engines, then the gas can be supplied to high-pressure propulsion engines, but the devices are expensive, generate sizable maintenance costs and induce vibrations in the ship
Solution Approach 1:
The gas supply system is divided into multiple independent circuits: a first gas supply circuit for high-pressure gas-consuming devices, a second gas supply circuit for low-pressure gas-consuming devices, and a gas return line. This segmentation allows each circuit to operate at its own optimal pressure level, eliminating the need for a single high-pressure compression system throughout the entire gas supply infrastructure.
Solution Approach 2:
The system allows gas to be supplied at different pressure levels depending on the specific needs of each gas-consuming device. High-pressure devices receive gas at 300 bar through the first circuit, while low-pressure devices receive gas at lower pressures through the second circuit, and excess vapor is handled through the return line at atmospheric pressure, optimizing overall system efficiency.
2Stress or pressure
If high-pressure compression devices are used to compress gas to 300 bar absolute, then the gas can be supplied to high-pressure propulsion engines, but maintenance costs increase significantly
Solution Approach 1:
The system compresses gas only to the extent necessary for each specific application. Instead of compressing all gas to 300 bar, the system compresses gas to the minimum required pressure for each device's needs, reducing wear and maintenance requirements on compression equipment while still meeting all operational requirements.
3Temperature
If a high-pressure pump is used to boil off liquid-state gas before sending it to the propel engine, then gas can be supplied to the engine, but the vapor-state gas (boil-off gas) that naturally forms in the tank cannot be removed
Solution Approach 1:
The gas return line acts as an intermediary pathway that collects excess vapor-state gas from the tank blanket and redirects it through heat exchangers where it can be condensed back to liquid state and returned to the cargo tank, preventing vapor accumulation while maintaining system efficiency.
4Loss of energy
If the efficiency of the gas supply system is increased by using vapor-state gas to improve condensation of excess vapor-state gas, then energy efficiency improves, but system complexity increases with additional heat exchangers and heat treatment branch
Solution Approach 1:
The heat treatment branch integrates with the existing gas return line infrastructure, combining the condensation function with the vapor removal function. The third heat exchanger is positioned within the gas return line system, allowing vapor-state gas to be cooled by colder vapor from the tank blanket in a unified flow path rather than requiring separate parallel systems.
Solution Approach 2:
The system uses its own vapor-state gas as the cooling medium for condensation. The colder vapor-state gas from the tank blanket serves as the refrigerant to condense the warmer excess vapor in the return line, eliminating the need for external power-consuming refrigeration systems and making the system self-sufficient.
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 enhances energy efficiency by up to 30% savings in electrical power consumption for vapor-state gas condensation and up to 45% for low-pressure gas consumption, while minimizing mechanical size and costs.
Implementation Method 1
the gas supply system comprising a third heat exchanger configured to implement a heat exchange between the vapor-state gas through the return line and the vapor-state gas through the heat treatment branch
Implementation Method 2
at least a first heat exchanger and at least a second heat exchanger, wherein each of them is configured to implement a heat exchange between the vapor-state gas flowing through the gas return line and the liquid-state gas flowing through the first gas supply circuit
Implementation Method 3
at least a high-pressure evaporator configured to evaporate the gas that flows through the first gas supply circuit
Data Source
AI summary
A supply system for supplying a high-pressure gas-consuming device and a low-pressure gas-consuming device includes: a first supply circuit, a second supply circuit, a return line, a first heat exchanger, a second heat exchanger, a heat treatment branch connected to the second supply circuit, and a third heat exchanger configured to operate a heat exchange between the gas flowing through the heat treatment branch and the gas flowing through the return line.