CO2 Purification by Liquefaction and Countercurrent Stripping
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Solution Overview
Problem
Existing methods for producing CO2 from process gas streams in heavy oil, petroleum coke, or coal gasification processes result in CO2 with impurities like N2, CO, and CH4, making it unsuitable for direct use in applications such as enhanced oil recovery.
Innovation Solution
Compressing CO2 to at least 60 bar and using gaseous CO2 as a stripping gas to remove impurities, followed by cooling and countercurrent passage through a stripping column to separate and purify CO2, ensuring it is in a liquid state and free of contaminants.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Quantity of substance
If CO2 is separated from process gas using physisorptive or chemisorptive absorption, then CO2 can be removed from the gas stream, but the CO2 produced contains 0.1 to 20 vol.% impurities (N2, CO, H2, CH4) and is not suitable for direct use
Solution Approach 1:
The patent applies parameter changes by compressing CO2 to high pressure (60-300 bar) and cooling to sub-zero temperatures to achieve liquefaction. This phase change enables selective separation where impurities remain gaseous while CO2 becomes liquid, achieving high purity without additional chemical treatment steps
Solution Approach 2:
The core invention utilizes phase transition of CO2 from gas to liquid state through compression and cooling. The impurities (N2, CO, H2, CH4) remain in gaseous phase while CO2 liquefies, allowing automatic separation. The liquid CO2 is then stripped with gaseous CO2 to remove any remaining trace impurities, achieving pharmaceutical-grade purity
2Manufacturing precision
If CO2 is compressed to high pressure and cooled for liquefaction, then CO2 purity is improved, but energy consumption increases
Solution Approach 1:
The patent combines the compression and cooling steps into an integrated process where the cooling medium is cooled CO2 itself from the same stream being purified. This internal heat exchange eliminates the need for external refrigeration systems, significantly reducing energy consumption while achieving the required purification and liquefaction
Solution Approach 2:
The process uses the CO2 stream itself as the cooling agent for its own liquefaction. The CO2 is cooled in countercurrent heat exchangers using colder CO2 from the process, creating a self-sustaining thermal cycle that minimizes external energy input required for compression and cooling
3Manufacturing precision
If CO2 is further purified to meet quality requirements for pressing and storage, then CO2 becomes suitable for direct use, but additional work steps are required
Solution Approach 1:
The patent extracts impurities from the CO2 stream by utilizing the phase difference between CO2 and impurities. During compression and cooling, CO2 liquefies while impurities remain gaseous and are automatically separated. A stripping column then removes any trace gaseous impurities from the liquid CO2, achieving the required purity for pressing and storage applications
Solution Approach 2:
Instead of removing impurities from gaseous CO2 through complex chemical absorption processes, the patent inverts the approach by liquefying CO2 and leaving impurities in the gas phase. This reverses the typical separation logic and achieves purification through physical phase separation rather than chemical treatment, simplifying the overall process
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 method achieves CO2 purity suitable for direct use, minimizing losses of valuable gases like CO and CH4, and enabling its storage in oil deposits.
Implementation Method 1
compressed to a pressure of at least 60 bar, absolute, or below the critical temperature of CO2 of 31 °C to at least 70 bar, absolute
Implementation Method 2
cooled to a temperature of -40 to -5° C
Implementation Method 3
the resulting predominantly gaseous impurities contained in CO2 in the liquid state are removed
Implementation Method 4
the vapor pressure of the contaminants to be removed from the liquid CO2 is greater than in the stripping gas and therefore a Transfer of the liquid CO2 into the stripping gas takes place
Implementation Method 5
stripping the CO2 with gaseous CO2 serving as a stripping gas and CO2 is obtained as a liquid
Implementation Method 6
recooled in order to condense out at least part of the CO2 from the stripping gas and return it to the bottom of the stripping column
Data Source
Figure 1
AI summary
The invention relates to a method for treating a process gas flow containing CO2 that is produced whilst producing pure synthesis gas from the crude gas of the process gas flow or during the partial oxidation of heavy olis, petroleum cokes and waste substances or during coal gasification or during the treatment of natural gas or gas which accompanies petroleum, from which CO2 is removed by physisorption or chemisorption and the solvent charged with CO2 is released at a low pressure for the desorption of the CO2. In order to produce CO2 as pure as possible, the unpurified CO2 is compressed at least at 60 bar[a] or below the critical temperature thereof to at least 70 bar[a] and the impurities contained in the liquid CO2 are removed by stripping with gaseous CO2 guided into the counter flow.