Analysis of the Characteristics of Decompression Capture of CO2 in Flue Gas by Cryogenic Heat

Abstract

To obtain the design and development guidelines for a cryo-capture system that combines an amine absorption method with a novel cryo-sublimation pump for recovering CO2 from flue gas using the cryogenic heat (−162 °C) of liquefied natural gas (LNG), we investigated the cooling, depressurization, and regeneration characteristics of CO2 through numerical analysis. We developed an unsteady lumped constant numerical model consisting of a regeneration tower, sublimation tank, and connecting passage. The numerical analysis investigated the effects of the partial pressure of CO2 in the inlet gas in the absorption tower, the CO2 regeneration rate in the regeneration tower, and the cooling wall area of the sublimation tank, on the temporal changes of various quantities in the process. The following findings were obtained as design and development guidelines: the interface area of CO2 regeneration tower SR should be a necessary and sufficient area where the integrated amount of dry ice production [Formula: see text] and the dry ice production efficiency η are as high as possible to make it compact and low-cost. At the same time, the area of the cooling wall SC is determined such that the sublimation and solidification capacity of CO2 is balanced with the CO2 regeneration capacity.

Keywords

• CO2 capture
• Decompression recovery
• Cryogenic heat
• Liquefied natural gas
• Dry ice
• Cryo-sublimation pump