Liquid Piston Compressor for Boil-Off Gas Utilization in LNG Storage
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Solution Overview
Problem
The challenge is to effectively manage boil-off gas from liquefied natural gas (LNG) storage tanks, as venting leads to economic and environmental losses, while re-liquefaction is complex and costly.
Innovation Solution
An apparatus comprising a storage tank, a liquid piston compressor, and a gas-fed device that compresses and utilizes boil-off gas, preventing environmental pollution and optimizing energy use by feeding compressed gas into an engine or fuel cell.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If boil-off gas is vented to the atmosphere, then pressure in the tank is maintained at safe levels, but environmental pollution occurs and economically valuable LNG is lost
Solution Approach 1:
The patent converts the harmful boil-off gas that would normally be vented into a useful fuel source by compressing it and feeding it to the engine, thereby eliminating environmental pollution and economic loss while maintaining tank pressure safety
Solution Approach 2:
The system uses the boil-off gas itself to serve dual purposes: maintaining tank pressure by removal and providing fuel for the engine, making the harmful byproduct beneficial to the system's operation
2Loss of substance
If boil-off gas is re-liquefied and returned to the tank, then LNG is conserved, but the process becomes technically complex and incurs large running costs
Solution Approach 1:
The patent extracts the boil-off gas from the tank and directs it to the engine fuel system, eliminating the need for complex re-liquefaction equipment while still preventing LNG loss by utilizing the gas productively
Solution Approach 2:
The patent introduces a compression system as an intermediary between the storage tank and the engine, simplifying the process compared to re-liquefaction while achieving the same goal of preventing LNG loss
3Productivity
If a compression system is added to compress boil-off gas, then gas can be utilized in the engine, but device complexity increases
Solution Approach 1:
The patent uses a liquid piston compressor that utilizes hydraulic principles, where liquid is fed into a cylinder to compress the gas, providing an efficient and relatively simple compression mechanism compared to traditional mechanical compressors
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 solution prevents environmental pollution, reduces economic losses, and increases the efficiency of LNG transport by utilizing boil-off gas as a fuel source, offering a cost-effective alternative to re-liquefaction.
Implementation Method 1
a liquid piston compressor disposed downstream of, and in fluid communication with, the storage tank and configured to receive boil-off gas from the storage tank and to compress the gas
Implementation Method 2
the apparatus comprises a pre-compressor. Preferably, the pre-compressor is disposed downstream of, and in fluid communication, with the storage tank
Implementation Method 3
Over time, this gradual introduction of heat causes some of the LNG to evaporate, or boil-off
Implementation Method 4
a gas-fed device disposed downstream of, and in fluid communication with, the liquid piston compressor, wherein the gas-fed device is configured to receive compressed gas from the liquid piston compressor
Data Source
AI summary
The invention provides an apparatus comprising a storage tank, a liquid piston compressor and a gas-fed device. The storage tank is configured to store liquefied gas therein. The liquid piston compressor is disposed downstream of, and in fluid communication with, the storage tank and is configured to receive boil-off gas from the storage tank and to compress the gas. The gas-fed device is disposed downstream of, and in fluid communication with, the liquid piston compressor, and is configured to receive compressed gas from the liquid piston compressor.