Cryogenic carbon capture (CCC) has attracted increasing attention for achieving very high CO2 capture efficiencies (>99%) with high product purity, without the use of chemical solvents or adsorbents. CCC relies on phase-change-based separation of CO2 from gas mixtures through either liquefaction or sublimation. Since CO2 does not form a liquid at atmospheric pressure, liquefaction-based CCC requires operation at elevated pressures (>30 bar), leading to significant material and energy costs. In contrast, desublimation-based cryogenic carbon capture (DCCC) operates at near-atmospheric pressure, avoiding the challenges associated with high-pressure systems. However, DCCC is often limited by dry ice deposition on cold surfaces, which can lead to fouling and often necessitate batch operation. In this work, a novel cryogenically cooled cyclone separator is developed and experimentally investigated to intensify the DCCC process and enable continuous operation without regeneration. The inherent swirl flow within the cyclone provides enhanced heat and mass transfer while facilitating the in situ separation and collection of desublimated CO2. Experiments were conducted to evaluate CO2 recovery as a function of inlet gas temperature, flow rate, and feed gas composition. The parametric study was carried out over a range of feed gas conditions: 250 to 333 K, 25 to 75 LPM, and 0.47 to 0.8 mole fraction of CO2, for a period of 40 min. A maximum experimental error of 4.6% was determined, accounting for instrumental and repeatability error. A maximum pressure drop of approximately 0.15 atm was measured. Theoretical analysis indicated that more than 99% of the pressure drop is due to the separation of CO2 from the feed gas stream rather than hydrodynamic losses. The results demonstrate high initial capture efficiency (>90%) for all experimental runs, followed by a gradual decline as dry ice accumulates on the separator walls, increasing heat and mass transfer resistances. The periodic detachment and collection of dry ice into the bottom collector of the cyclone were observed at 20 and 30 min. This detachment enhanced CO2 recovery, resulting in a cyclic yet continuous capture process. The results of this study were compared to those of reported studies on axial-flow-based DCCC, and an approximately 2.8-fold increase in the mass of CO2 captured per unit heat transfer area was observed. The proposed intensified DCCC method would be useful for feed gas with a high CO2 concentration and for high throughputs.
Kurian et al. (Thu,) studied this question.