LNG Carrier Tank Management for Boil-Off Gas Allocation
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Solution Overview
Problem
Existing methods for managing boil-off gas (BOG) in liquefied gas transport vessels result in significant losses and inefficiencies, as excess BOG is burned without benefit, and there is a need to minimize BOG generation and utilization for propulsion.
Innovation Solution
A computer-implemented method and system that utilizes weather forecasts and operational models to estimate BOG generation, generate tank management scenarios, and display scenarios based on a cost function to optimize BOG utilization and minimize losses.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Use of energy by moving object
If BOG is sent to the propulsion engine, then energy utilization is improved, but the amount of BOG delivered to destination is reduced
Solution Approach 1:
The system dynamically adjusts BOG allocation between propulsion engine and destination delivery based on real-time conditions including weather forecasts, vessel speed, and tank pressure. The vapor phase treatment system continuously optimizes the split of BOG flow to balance energy recovery needs with delivery requirements, rather than using a fixed allocation strategy.
Solution Approach 2:
The system changes operational parameters such as tank pressure, temperature, and BOG extraction rates to optimize both propulsion engine performance and BOG delivery. By adjusting these parameters dynamically, the system can maximize energy utilization while preserving sufficient BOG quantity for destination delivery.
2Reliability
If excess BOG is burned in the gas combustion unit, then safety is improved, but energy loss increases
Solution Approach 1:
The system implements continuous feedback monitoring of tank pressure, temperature, and BOG generation rates. Based on this feedback, the vapor phase treatment system dynamically adjusts BOG extraction and directs appropriate amounts to the propulsion engine versus the gas combustion unit, minimizing unnecessary burning while maintaining safety.
Solution Approach 2:
The system uses weather forecasts and voyage information to predict future BOG generation patterns in advance. This preliminary information allows the system to proactively optimize BOG management strategies, reducing the need for emergency burning in the gas combustion unit by preparing appropriate BOG allocation plans beforehand.
3Loss of substance
If tank pressure is increased to reduce BOG generation, then BOG loss is reduced, but propulsion engine performance may be affected
Solution Approach 1:
The system dynamically adjusts tank pressure and BOG extraction rates based on real-time conditions and predictive weather data. By optimizing these parameters continuously, the system reduces BOG generation losses while ensuring sufficient BOG supply to the propulsion engine for maintaining required power output.
Solution Approach 2:
The system changes operational parameters including tank pressure, temperature, and BOG extraction timing to minimize BOG generation. These parameter changes are optimized to balance reduction in BOG losses with maintenance of propulsion engine performance 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
The method and system provide decision-making assistance by optimizing BOG management, reducing the amount burned and enhancing propulsion efficiency by strategically utilizing BOG, thereby minimizing losses and improving vessel operations.
Implementation Method 1
the vapor phase treatment system further being capable of extracting a portion of the liquid phase contained in the tank and of evaporating this portion in order to send it to the propulsion engine
Implementation Method 2
despite the thermal insulation of the tanks. The gas that is generated due to this heating is commonly called boil-off gas
Data Source
AI summary
A method for assisting the management of a vessel comprising at least one tank configured to contain liquefied gas and a vapor phase treatment system capable of sending boil-off gas exiting the tank to a propulsion engine of the vessel or to a gas combustion unit on board the vessel and capable of extracting a portion of the liquid phase contained in the tank and of evaporating this portion in order to send it to the propulsion engine. The method comprises: generating at least one tank management scenario defining an evolution of the pressure of the gas phase contained in the tank along a path of the vessel; computing a cost function that at least depends on a total amount of boil-off gas generated in the tank along the path; and displaying to a user the tank management scenario as a function of the computed cost function.