Liquid CO2 Sub-Cooling Using Nitrogen Heat Exchange
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Solution Overview
Problem
Existing methods for sub-cooling liquid CO2 suffer from inefficiencies, such as pressure variations leading to flow rate disturbances, gas creation, and energy loss, making them costly and environmentally impactful.
Innovation Solution
A process utilizing heat exchange between liquid CO2 and liquid nitrogen to sub-cool CO2, leveraging existing nitrogen demand on-site to recover and reuse cold energy, with a circulator ensuring efficient fluid circulation and temperature control.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Temperature
If liquid CO2 is sub-cooled using conventional mechanical cooling, then the temperature is reduced, but energy consumption increases and cost rises
Solution Approach 1:
The patent converts the waste cold energy from nitrogen vaporization (which would otherwise be lost) into a useful cooling resource for sub-cooling CO2. The nitrogen evaporation process, typically a loss, is harnessed to pre-cool CO2 before it enters the mechanical cooling system, reducing the energy burden on compressors and refrigeration units.
Solution Approach 2:
The patent merges two separate processes - nitrogen vaporization and CO2 sub-cooling - into a integrated heat exchange system. The cold stream from nitrogen evaporation is combined with the CO2 cooling process through heat exchangers, creating a coupled system that achieves mutual benefit and reduces overall energy consumption.
2Productivity
If liquid CO2 is sub-cooled to increase dry ice production yield, then productivity improves, but additional energy consumption is required
Solution Approach 1:
The patent applies preliminary cooling action to CO2 before it enters the mechanical refrigeration system. By using waste nitrogen cold energy to pre-sub-cool CO2, the subsequent mechanical cooling requires less energy to achieve the same final temperature, thereby increasing dry ice production efficiency without proportional energy increases.
3Temperature
If pressure of liquid CO2 is reduced to sub-cool it, then temperature decreases, but flow rate becomes unstable due to pressure variations
Solution Approach 1:
The patent introduces heat exchangers as intermediary devices that enable temperature reduction through heat transfer rather than direct pressure reduction. This intermediary approach allows CO2 to be sub-cooled while maintaining stable pressure and flow conditions, avoiding the flow instability that would result from direct pressure reduction.
4Temperature
If mechanical cooling is used to sub-cool CO2, then temperature is reduced, but system complexity and cost increase
Solution Approach 1:
The patent makes the nitrogen storage system multi-functional by having it serve both its original purpose (providing gaseous nitrogen) and an additional function (providing cold energy for CO2 sub-cooling). This eliminates the need for dedicated sub-cooling equipment, reducing system complexity and avoiding additional capital investment.
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
Enhances CO2 sub-cooling efficiency, reduces carbon footprint, and increases dry ice production yield without additional energy consumption, while maintaining system integrity and reducing costs.
Implementation Method 1
heat exchange in an exchanger with liquid nitrogen taken from a nitrogen storage tank
Implementation Method 2
when there is consumption of nitrogen but no consumption of CO2, first cooling of liquid CO2 taken from the CO2 storage tank is carried out by heat exchange with liquid nitrogen
Data Source
AI summary
A process for supplying sub-cooled liquid CO2 to a site comprising a user station for the liquid CO2, from a liquid CO2 storage tank, which site contains a source of liquid nitrogen that is able to supply gaseous nitrogen to a user station for the gaseous nitrogen.