CO2 Removal Tower Segmentation for Purity
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Solution Overview
Problem
The existing CO2 removal sections in hydrogen-containing synthesis gas plants produce a CO2 stream with undesirable hydrogen and impurity content, which contaminates the purified CO2, making it unsuitable for industrial use, particularly in ammonia-urea synthesis and the food industry, and require additional equipment and capital costs for separate pressure vessels.
Innovation Solution
A revamped CO2 removal section with sealing means that isolates and separates the hydrogen-rich and hydrogen-free CO2 streams during regeneration, using a partitioned tower with a hydraulic seal to prevent backflow and contamination, allowing for separate export of streams with different hydrogen contents, eliminating the need for separate pressure vessels.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Device complexity
If flashing and stripping are performed in a single tower without separation, then device complexity is reduced, but the CO2 stream becomes contaminated with hydrogen and impurities
Solution Approach 1:
The single tower is segmented into two distinct functional zones: an upper flashing zone and a lower stripping zone. The flashing zone produces a hydrogen-rich CO2 stream that is separately exported, while the stripping zone produces a high-purity CO2 stream. This segmentation allows both streams to be generated in one vessel without requiring separate pressure vessels, thus maintaining low device complexity while achieving high CO2 purity.
Solution Approach 2:
The hydrogen-rich first stream is extracted and separated from the tower at the flashing zone, preventing it from contaminating the high-purity CO2 stream produced in the stripping zone. This extraction of the harmful hydrogen-containing stream resolves the contradiction by removing the contamination source while maintaining the integrated tower structure.
2Device complexity
If the first stream is mixed with the second stream, then device complexity is reduced, but hydrogen content in exported CO2 increases
Solution Approach 1:
The first stream containing hydrogen is extracted and separately exported from the tower through dedicated outlets in the flashing zone. This prevents the hydrogen from mixing with and contaminating the second high-purity stream, thereby eliminating the harmful effect of hydrogen in the exported CO2 without requiring additional separation equipment.
Solution Approach 2:
The tower is segmented into distinct flashing and stripping zones with separate outlet systems. This segmentation enables independent export of the hydrogen-rich first stream and the high-purity second stream, preventing contamination while maintaining a single integrated vessel structure.
3Manufacturing precision
If separate pressure vessels are used for flashing and stripping, then CO2 purity is improved, but capital cost increases
Solution Approach 1:
The flashing zone and stripping zone are merged into a single integrated pressure vessel rather than using separate vessels. The tower is designed with internal zoning that allows both functions to operate simultaneously in one container, reducing capital costs while maintaining the purity benefits of separate stream handling through dedicated outlets for each zone.
Solution Approach 2:
While merging the vessels, the internal structure is segmented into distinct flashing and stripping zones with separate outlet systems. This internal segmentation ensures that the hydrogen-rich first stream and high-purity second stream remain separate throughout the process, achieving CO2 purity without requiring multiple external pressure vessels.
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 effectively produces a low-hydrogen, high-purity CO2 stream suitable for various industrial applications without increasing capital costs, enhancing the value of the exported CO2 and ensuring safety by reducing explosive mixture risks.
Implementation Method 1
an absorption section wherein carbon dioxide is removed from the synthesis gas by absorption in an absorbing solution
Implementation Method 2
The loaded solution is first flashed in the flashing zone to a relative pressure of 0.2 to 1 bar(g). Said flashing causes the release of about 15-25% of the carbon dioxide originally contained in the loaded solution
Implementation Method 3
The so obtained semi-lean solution is then subjected to stripping in the underlying stripping zone where the remaining 75-85% of the carbon dioxide is released
Data Source
AI summary
A method for revamping a CO2 removal section for removing carbon dioxide from a hydrogen-containing synthesis gas, wherein the CO2 removal section comprises an absorption section (2) wherein carbon dioxide is transferred to an absorbing solution and a stripping tower (3) for regeneration of the CO2-loaded solution, said stripping tower comprising an upper zone (4) where a first gaseous CO2 stream (10) and a partially regenerated semi-lean solution (11) are produced, and a lower zone (5) acting as a stripping zone where a second gaseous CO2 stream (12) and a lean regenerated solution are produced, the second CO2 stream (12) being a substantially pure stream containing less hydrogen and impurities than the first CO2 stream, and wherein the method of revamping provides the installation of sealing means (16) inside the stripping tower (3), arranged to isolate said second gaseous CO2 stream (12) from the first stream (10), so that the second stream (12) can be exported separately.