LCO2 Offloading Vapor Return System for Cross-Contamination Prevention
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Solution Overview
Problem
Existing CCS systems face challenges in maintaining pressure and preventing cross-contamination of CO2 carrier ships due to impurities in the vapor phase returned from onshore intermediate storage tanks, which can disrupt the carbon capture and storage process.
Innovation Solution
A system that utilizes a slip stream of CO2 withdrawn from an offloading stream to vaporize and return CO2 vapors to the ship, while sub-cooling the CO2 stream from the intermediate storage tank by respraying it into the tank's headspace, thereby avoiding contamination and maintaining pressure without returning potentially impure vapors.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Stress or pressure
If vapor from onshore intermediate storage tanks is returned to CO2 carrier ships for pressure maintenance, then pressure control in both tanks and ships is improved, but cross-contamination occurs due to impurities in the vapor phase from previous cargo
Solution Approach 1:
The system segments the vapor return process by introducing an intermediate vaporization chamber that separates the onshore storage tank vapor from the carrier ship cargo tank. The vapor from the onshore tank is first directed to the vaporization chamber where it is mixed with cold CO2, and only the resulting cold CO2 vapor is returned to the carrier ship, preventing direct return of potentially contaminated vapor.
Solution Approach 2:
The invention introduces cold CO2 from the cold box as an intermediary substance that mixes with the vapor from the onshore intermediate storage tank in the vaporization chamber. This intermediary cold CO2 acts as a barrier that prevents direct contact between the onshore vapor and the carrier cargo, while still enabling pressure maintenance through the returned cold vapor mixture.
2Stress or pressure
If a vapor return connection is established between onshore storage and carrier ship, then pressure maintenance in both systems is achieved, but the system complexity increases
Solution Approach 1:
The invention merges the vapor return function with the existing cold box and evaporator system. The cold CO2 from the cold box is routed through the evaporator to generate cold vapor, which then serves dual purposes: maintaining pressure in the onshore storage tank and providing cold vapor for return to the carrier ship, eliminating the need for separate vapor return infrastructure.
Solution Approach 2:
The evaporator and vaporization chamber serve multiple functions: they cool the CO2 from the onshore storage tank, generate cold CO2 vapor for pressure maintenance, prevent cross-contamination through the vaporization process, and provide the cold vapor return stream to the carrier ship. This multi-functionality reduces overall system complexity despite the added vapor return capability.
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 ensures pressure maintenance in both ship and storage tank systems while preventing cross-contamination, reducing energy requirements, and eliminating the need for a BOG-handling system by generating vapors directly from off-loaded cargo, ensuring a clean vapor return independent of onshore storage contents.
Implementation Method 1
A slip stream of LCO2 withdrawn from a stream of LCO2 being offloaded to the terminal is vaporised
Implementation Method 2
the vaporisation is used to provide sub-cooling of an LCO2 stream withdrawn from the intermediate LCO2 storage tank
Implementation Method 3
a resulting sub-cooled LCO2 stream is returned to the intermediate LCO2 storage tank by spraying into the head space of the intermediate LCO2 storage tank
Implementation Method 4
the resulting CO2 vapour after compression thereof is led back to the ship
Data Source
Figure 1
AI summary
A system 250 for offloading LCO2 from an LCO2 carrier ship 30 to an intermediate LCO2 storage tank 40 at an LCOz receiving terminal 300 connected to a long term LCO2 storage facility 120 is disclosed, which system avoids cross-contamination from cargo of one ship to another, wherein a slip stream of LCO2 withdrawn from a main stream of LCO2 being offloaded to the terminal 100 is vaporised and returned to the LCO2 carrier ship 30, and the vaporisation is used to provide sub-cooling of an LCO2 stream withdrawn from the intermediate LCO2 storage tank 40, and wherein a resulting sub-cooled LCO2 stream is returned to the intermediate LCO2 storage tank 40 by spraying into the head space of the intermediate LCO2 storage tank. A corresponding method is also disclosed.