Dual-purpose cryogenic tank stripping with localized bottom heating
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Solution Overview
Problem
The transition process between storing LNG and LIN in dual-use tanks is inefficient due to the need to completely remove LNG before loading LIN, resulting in prolonged heating times to vaporize residual LNG, which increases the time the LNG carrier is not transporting LNG or LIN, affecting profitability.
Innovation Solution
A method involving a first pump to empty a portion of the cryogenic liquid, focusing the remaining liquid at the tank's bottom, and a second pump to evacuate it, followed by localized heating to vaporize the residual liquid, reducing the need to heat the entire tank.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the entire tank is heated to vaporize residual LNG, then complete removal of LNG is achieved, but the heating time is excessively long
Solution Approach 1:
The patent applies local quality by concentrating the heating action only in the bottom region of the tank where residual LNG accumulates, rather than heating the entire tank. The heating element is positioned at the bottom to directly contact and vaporize the residual liquid, achieving complete LNG removal while significantly reducing the heating time and energy required.
2Loss of substance
If the tank is heated above LNG liquefaction temperature to vaporize residual LNG, then all LNG can be removed, but the cooling time to reach LIN transport temperature increases
Solution Approach 1:
The heating operation is localized to the bottom region where residual LNG is concentrated, minimizing the volume of liquid heated above the LNG liquefaction temperature. This localized approach reduces the thermal mass that subsequently needs to be cooled, thereby shortening the cooling time required to reach the LIN transport temperature of -196°C.
Solution Approach 2:
The patent extracts the residual LNG from the main tank body by concentrating it at the bottom through the stripping line configuration, then applies heating only to this extracted portion. This separation allows the heating action to be confined to a small volume, reducing the overall thermal impact and subsequent cooling requirements for the entire tank.
3Adaptability or versatility
If dual-use tanks are used to transport both LNG and LIN, then carrier versatility is improved, but the transition time between cargoes increases
Solution Approach 1:
The stripping system is designed with localized heating at the tank bottom that targets only the residual LNG in the bottom region. This localized approach allows for rapid vaporization and removal of residual cargo, enabling faster transition between LNG and LIN cargoes while maintaining the dual-use capability of the tanks.
Solution Approach 2:
The stripping line configuration and bottom heating system perform preliminary removal of residual LNG before the main cargo loading operation begins. This preliminary action ensures that the tank is ready for the next cargo without requiring extended heating or cooling periods, thereby improving turnaround speed while maintaining versatility.
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 significantly shortens the time required to transition the tank from LNG to LIN storage, potentially reducing the preparation time by 30-50% compared to existing methods, thereby increasing operational efficiency and profitability.
Implementation Method 1
A focused heating structure delivers heat only to the location. The delivered heat raises the temperature of the residual portion above the liquefaction temperature of the cryogenic liquid, thereby vaporizing all of the residual portion.
Implementation Method 2
The delivered heat raises the temperature of the residual portion above the liquefaction temperature of the cryogenic liquid, thereby vaporizing all of the residual portion.
Data Source
Figure 1~2
Figure 3A~3C
Figure 3D~3E
AI summary
An apparatus and method of storing and transporting, in a dual-use cryogenic storage tank, a cryogenic liquid having a liquefaction temperature. A first pump empties the tank of a first portion of the cryogenic liquid, thereby leaving a second portion of the cryogenic liquid in the cryogenic storage tank. A second portion of the cryogenic liquid is focused at a location on a bottom of the cryogenic storage tank. Using a second pump located at the location, the cryogenic storage tank is emptied of the second portion of the cryogenic liquid, whereby a residual portion of the cryogenic liquid is left therein. Using a focused heating structure, heat may be delivered to the location to raise the temperature of the residual portion above the liquefaction temperature, thereby vaporizing all of the residual portion.