Process and device for distilling carbon dioxide
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Solution Overview
Problem
The production of food-grade CO2 requires advanced purification of liquid CO2, which is energy-intensive and costly, particularly in cryogenic capture processes where optimizing the distillation step to eliminate hydrocarbons like ethane is crucial for reducing costs and energy consumption.
Innovation Solution
A process and apparatus that reduce energy consumption in liquid CO2 distillation by optimizing the distillation column operations, including compression, cooling, partial condensation, and intermediate extraction of a partially purified CO2 stream, which reduces the quantity of reboiling gas and overhead gas flow, thereby minimizing energy use and CO2 losses.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If advanced purification of liquid CO2 is performed through distillation to eliminate hydrocarbons, then the purity of CO2 is improved, but the energy consumption increases
Solution Approach 1:
The distillation column is divided into multiple theoretical plates (at least 10), creating segmented stages for progressive purification. This segmentation allows CO2 to be purified incrementally as it rises through the column, achieving high purity without requiring excessive energy input at any single stage.
Solution Approach 2:
The invention uses partial condensation of the compressed gas mixture rather than complete condensation, followed by distillation. This partial action approach achieves the necessary purification while avoiding the excessive energy consumption that would result from complete condensation and total reboiling.
Solution Approach 3:
The process changes physical parameters systematically: compressing the gas mixture to increase pressure, partially condensing to create liquid-vapor equilibrium, and using the resulting temperature and concentration gradients in the distillation column. These parameter changes enable efficient separation without excessive energy input.
2Manufacturing precision
If the quantity of reboiling gas injected at the bottom of the distillation column is increased to improve separation efficiency, then the purity of CO2 increases, but the energy consumption increases
Solution Approach 1:
The system uses itself to provide the necessary energy for separation. The compressed gas mixture that is being cooled serves as the heat source for vaporizing liquid CO2 at the bottom of the column. This self-service approach eliminates the need for external reboiling energy input while maintaining effective separation.
Solution Approach 2:
The heat exchanger acts as an intermediary that transfers thermal energy from the compressed gas mixture to the liquid CO2 at the column bottom. This intermediary mechanism enables energy transfer within the system without requiring external energy input, achieving vaporization through internal heat exchange.
3Manufacturing precision
If the distillation column operates with complete condensation and total reboiling to maximize purification, then the purity of CO2 is improved, but the quantity of CO2 losses increases
Solution Approach 1:
The invention recovers CO2 that would otherwise be lost. The overhead gas from the distillation column, which contains CO2, is compressed and fed back into the system rather than being discarded. This recovery approach minimizes CO2 losses while maintaining purification efficiency.
Solution Approach 2:
The process maintains continuous operation without complete shutdowns for purification cycles. The distillation column operates continuously with steady-state separation, and the recycled overhead gas ensures continuous purification without interrupting the process or causing material losses associated with batch operations.
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 reduces energy consumption and increases the yield of CO2 production by minimizing the quantity of vaporized CO2 injected into the column and reducing CO2 losses, enhancing the efficiency of the CO2 capture process.
Implementation Method 1
i) compression of the gas mixture in a compressor to produce a gas mixture to be cooled
Implementation Method 2
ii) cooling and partial or total condensation of the gas mixture so as to obtain a liquid flow enriched in CO2
Implementation Method 3
ii) cooling and partial or total condensation of the gas mixture so as to obtain a liquid flow enriched in CO2
Implementation Method 4
iii) sending of the liquid flow enriched in CO2 or a liquid flow formed by enriching the enriched liquid flow even more in CO2 into an upper part of a distillation column to separate said liquid flow into a gas enriched in the at least one lighter component and depleted in CO2 at the top of the column and a liquid rich in CO2 at the bottom of the column
Implementation Method 5
vii) extraction of a partially purified liquid CO2 stream at an intermediate level of the column at least one theoretical plate below the top of the column and at least one theoretical plate above the bottom of the column and vii) vaporization of the stream extracted at the intermediate level of the column by heat exchange with the gas mixture which is cooled in step ii)
Implementation Method 6
vii) vaporization of the stream extracted at the intermediate level of the column by heat exchange with the gas mixture which is cooled in step ii)
Data Source
AI summary
In a process for distilling a gas mixture of CO2 and at least one component lighter than CO2, a partially purified liquid CO2 stream is withdrawn at an intermediate level of the distillation column at least one theoretical plate below the top of the distillation column and at least one theoretical plate above the bottom of the distillation column and the stream extracted at the intermediate level of the distillation column is vaporized by heat exchange with the gas mixture, with which it is then compressed.