Abstract
This work expands upon previous work on a moving bed cryogenic carbon capture (CCC). Cryogenic carbon capture using a fixed packed bed captures CO2 frost deposited on the surface of the bed material; this build-up of frost fouls the heat transfer of the capture column and requires periodic shut down of the process to regenerate the bed material and collect CO2 for further storage. Using a moving bed continuously removes frosted bed material from the capture column preventing the excessive build-up of frost and eliminating the need for a regeneration step within the capture column. This paper sets out two objectives in evaluating an experimental moving bed system with a fixed volume of bed material; i) compare two different types of bed material within the capture column, a high-density ceramic and a steel bed material of similar particle sizes, and ii) combine the precooling step and capture step within the cryogenic capture column to allow the cooling of bed material and CO2 frost formation simultaneously. Frost front velocity results for the two different bed materials show 0.78 mm/s for steel bed material and 1.81 mm/s for ceramic bed material. Introducing a vertical gas injector into the capture column for additional cooling during the capture step allowed the capture step to be extended to approximately 5 minutes of continuous CO2 capture.
Highlights
This work expands upon previous work on a moving bed cryogenic carbon capture (CCC)
The use of a moving bed addresses the limitation of fixed packed bed Cryogenic carbon capture (CCC) by preventing the accumulation of CO2 frost within the capture column without requiring multiple capture columns or evaporators to operate cyclically, instead the CO2 frost covered bed material is removed from the capture column to be regenerated and is recirculated into the capture column
A slightly higher frost front velocity is expected from the ceramic bed material due to the lower density of ceramic compared to steel
Summary
This work expands upon previous work on a moving bed cryogenic carbon capture (CCC). Cryogenic carbon capture using a fixed packed bed captures CO2 frost deposited on the surface of the bed material; this build-up of frost fouls the heat transfer of the capture column and requires periodic shut down of the process to regenerate the bed material and collect CO2 for further storage. Similar to the circulation of a contact fluid, the solid bed material can circulate creating a moving bed in order to prevent the excessive accumulation of CO2 frost in the capture column with the added advantages of avoiding gas compression costs by operating close to atmospheric pressure and providing a simple separation stage subliming CO2 frost present on a moving bed material comparatively to separation of a slurry of CO2 frost and contact liquid. The results of previous experimental work has demonstrated the potential of the A3C process with the moving bed able to control the excessive accumulation of CO2 on the frosted bed material [11], showing the potential for the process to continuously capture CO2 It highlighted the requirement of combining the cooling step and the capture step within the capture column, allowing both to occur simultaneously. Addressing the need to perform the multiple stages of the CCC cycle simultaneously, this work performs the precooling step of the bed material and the capture step simultaneously as a first step towards a continuous process
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