LPG Carrier Reliquefaction System Using Cross-Cargo Heat Exchange
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Solution Overview
Problem
Existing LPG carriers require multiple reliquefaction units to handle two different cargoes, leading to excessive capacity and intermittent operation due to segregated handling of vapors, which increases the number of units needed and operational complexity.
Innovation Solution
A method and system that uses a minimum of two reliquefaction units, where vapor from one cargo type is condensed and passed through a heat exchanger to condense vapor from a second cargo type, reducing the number of units required and utilizing condensed vapor as a refrigerant, with optional throttling, compression, and separation to manage pressure and flow.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If multiple reliquefaction units are installed to handle two different LPG cargoes simultaneously, then the cargo vapor condensation capability is improved, but the number of units exceeds actual operational needs and increases device complexity
Solution Approach 1:
The patent makes a single reliquefaction unit capable of handling vapors from different cargo types (propane and butane) by equipping it with multiple heat exchangers that can process vapors from different cargo tanks. The unit can switch between handling propane vapor, butane vapor, or both simultaneously, eliminating the need for separate dedicated units for each cargo type while maintaining full condensation capability.
Solution Approach 2:
The patent combines the functions of multiple dedicated reliquefaction units into a single multi-functional unit. By merging the vapor handling capabilities for different cargo types into one unit with multiple heat exchangers, the system reduces the total number of reliquefaction units from three or four to just one or two, while maintaining the ability to handle all cargo vapors effectively.
2Reliability
If dedicated reliquefaction units are assigned to each cargo type, then the cargo handling reliability is improved, but the operational complexity and intermittent operation increase
Solution Approach 1:
The patent introduces dynamic flexibility by allowing a single reliquefaction unit to adapt its operation mode based on real-time cargo requirements. The unit can dynamically switch between handling different cargo types and can operate in various configurations (handling one cargo type at a time, or both simultaneously), eliminating the rigidity of dedicated units and reducing operational complexity.
Solution Approach 2:
The multi-functional reliquefaction unit can perform the duties of multiple dedicated units, handling vapors from different cargo types as needed. This universality allows the system to maintain high reliability for each cargo type while simplifying operational procedures, as a single unit can be controlled to serve different cargo handling needs without requiring complex coordination between multiple dedicated units.
3Stability of the object's composition
If segregated vapor handling is implemented for different cargo types, then the cargo purity is maintained, but the number of reliquefaction units and system complexity increase
Solution Approach 1:
The patent segments the vapor handling process within a single reliquefaction unit by providing separate heat exchangers for different cargo types. Each heat exchanger can process vapors from specific cargo tanks independently, maintaining cargo purity and preventing mixing, while all these segmented processes are coordinated within one integrated reliquefaction unit rather than requiring separate dedicated units for each segment.
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 minimizes the number of running reliquefaction units, reduces operational time, and maintains required refrigeration capacity, allowing for flexible installation and efficient handling of vapors from multiple cargo types, while meeting international standards and ship owner requirements.
Implementation Method 1
passing the condensed vapor through a heat exchanger so as to simultaneously flow vapor from a second cargo type through the heat exchanger and condense the vapor from the second cargo type by heat exchanging with the condensed vapor from the first cargo type
Implementation Method 2
reliquefaction units in which vaporized gases are condensed and then returned into at least one cargo tank for the respective LPG cargo type
Data Source
AI summary
A method for storage and transport of LPG on LPG carriers, in particular two cargoes of different LPG types on same shipment, having reliquefaction units in which vaporized gases are condensed and then returned into at least one cargo tank for the respective LPG cargo type. The method is further comprising: using the reliquefaction units, at a minimum one running, as to condense vapour from the first cargo type; passing the condensed vapour through a heat exchanger; simultaneously flowing vapour from the second cargo type through the heat exchanger as to condense vapour by means of heat exchanging with the condensed vapour; and returning the condensed vapours leaving the heat exchanger back into the respective cargo types. The present invention is also disclosing a system for storage and transport of LPG on LPG carriers.