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The Potassium-based dry sorbent CO 2 capture process can selectively capture CO 2 from flue gas without toxicity. In this study, the optimization of regeneration condition was investigated to pursue economical CO 2 capture process in a circulated fluidized bed reactor as most energy for CO 2 capture is consumed in the sorbent regeneration. One important part for CO 2 capture process is to produce highly concentrated CO 2 during the sorbent regeneration in the conditions of CO 2 rich with a presence of H 2 O, which thermodynamically reduces the sorbent regeneration efficiency at low temperature. This could be overcome by increasing the regeneration temperature although the sorbent regeneration energy increases. The dry sorbent performance in the carbonator was evaluated by changing the temperature, CO 2 and H 2 O concentration in the regenerator, which showed about 88% CO 2 removal efficiency and 5.6 wt% dynamic sorption capacity. The dry sorbent was sampled at each operating condition to confirm the dry sorbent performance, evaluated over CO 2 concentration. The optimal regeneration condition was obtained by considering CO 2 removal efficiency, dynamic sorption capacity and regeneration energy. Finally, the optimal regenerator temperature was determined to be approximately 468 K where the CO 2 capture process in the circulated fluidized bed reactor showed 95% for CO 2 purity. Image 1 • Highest CO 2 removal efficiency was obtained as 88% in a CFB reactor. • Effect of H 2 O during regeneration was negligible on sorbent performance. • Comparable sorbent performance observed even at high concentration CO 2 condition. • Optimal regenerator temperature was determined to be around 468 K. [ABSTRACT FROM AUTHOR]

Dry sorbent CO 2 capture process is a proven technology to remove CO 2 efficiently from flue gas. The current system was used to understand the effect of solid inlet height (H in) and horizontal heat transfer tubes on solid hydrodynamics in the fast fluidized bed (FFB). Also, the ranges of stable hydrodynamic conditions were visually confirmed at the varied H in , gas velocity (U g) and solid circulation rate (G s). The changes in the suspension density (ρ sus) during CO 2 carbonation reaction was experimentally measured and matched to the ρ sus at the specific gas velocity under no reaction bed. It showed that the ρ sus at the initial U g = 1.4 m/s under the reaction mode increased to that at 1.04 m/s along the bed due to the carbonation reaction. Heat transfer coefficients (HTC) were obtained during CO 2 carbonation operation over 80 h, which resulted in CO 2 removal efficiency (85%) and CO 2 purity (96%). Finally, the effect of ρ sus was determined to be the most significant factor on HTCs, ranged from 135 to 215 W/m2∙oC during the carbonation reaction. It indicated that the different local HTCs at different bed heights were observed at the carbonation or no reaction modes due to the exothermic reaction heat. Image 1 • Hydrodynamics in FB reactor during CO 2 carbonation reaction was investigated. • Over 80 h of carbonation reaction was conducted. • Above 84% average CO 2 removal efficiency with 95% CO 2 purity was achieved. • Suspension density and T cw in FB reactor were important factors determining HTC. • Higher HTC was ranged from 135 to 215 W/m2-oC at different conditions. [ABSTRACT FROM AUTHOR]

[Display omitted] • The working capacity and stability of absorbent were studied for CO 2 capture. • MPS-supported epoxide-functionalization of PEHA absorbent was synthesized. • PO-PEHA/MPS adsorbent exhibited the working capacity of 1.8 mmol g−1 in 20 cycle. • When the adsorption time was reduced, the regeneration heat was 2.86 GJ tCO 2 -1. • Adsorbent that is regenerated in 100% CO 2 , not inert (N 2 , He) conditions was developed. N -functionalized solid adsorbents have been studied for post-combustion CO 2 capture. Most studies have focused only on the adsorption condition of the adsorbents. Few studies have focused on the regeneration condition of adsorbents. Regeneration is required under the condition of 100 % CO 2 for high-purity CO 2 separation. Regeneration under inert conditions such as N 2 or He, not under the condition of 100 % CO 2 regeneration are required additional cost for high-purity CO 2 separation. In this study, a macroporous silica (MPS) support, which combined a high surface area, large porosity and large pore volume, was selected as the support to achieve high CO 2 capture performance. Pentaethylenehexamine (PEHA) was selected because of its high amine content, high adsorption capacity, high thermal stability, and low cost. The epoxide functionalization of PEHA was used to suppress the urea formation under regeneration conditions. The working capacity and cyclic stability of epoxide functionalization of MPS-based PEHA adsorbents were investigated. A working capacity of 1.8 mmol g−1 was maintained by repeating adsorption and desorption experiments 20 times under an adsorption condition of 15 % CO 2 and a desorption condition of 100 % CO 2. Additionally, the stability of the adsorbent under a 100 % CO 2 regeneration condition was confirmed by maintaining the working capacity constant during 20 repeated adsorption and desorption cycle experiments. When the adsorption time was reduced to minimize H 2 O adsorption, the regeneration heat of the adsorbent was 2.86 GJ tCO 2 -1. These results demonstrated that the regeneration ability was excellent under the condition of 100 % CO 2 , which is the actual process application condition. This approach is promising for industrial applications of CO 2 capture technology. [ABSTRACT FROM AUTHOR]

3 MWth scale chemical looping combustion (CLC) system using circulating fluidized bed (CFB) is being developed as a liquidized natural gas power generation technology to reduce CO 2 emissions. Dipleg, considered a blood vessel of CFB, conveys solids captured by cyclone to the fluidized bed while preventing gas mixing. This vertical passage plays key role in solids circulation and cyclone performance in thousands of CFB systems, yet only a limited information is available on its design and operation. This study experimentally investigated the flow characteristics in dipleg to verify design and operating conditions for smooth solid flow while predicting the amount of gas mixing. When solid circulation rate increased, both upward and downward gas flowrates in dipleg increased. It was found that the sum of two flowrates were equal to the volumetric flowrate of solids in the dipleg. Unstable operation occurred when 1) the gas-solid relative velocity in the dipleg became higher than the minimum slugging velocity, and 2) bubble diameter in bubbling bed became larger than the dipleg diameter. Finally, models for operation range and the amount of gas mixing in dipleg were proposed, and the design and operation range of the dipleg in 3 MWth scale CLC was suggested. Gas flows and design range of a dipleg in 3 MWth chemical looping combustor derived in this study. [Display omitted] • Applicability of dipleg in CFB was investigated and design factors were confirmed. • The amount of up- and down-stream gas was measured within dipleg. • Almost same amount of gas was exchanged with the down-stream particles. • Slugging in dipleg interfered the solid flow. • Bubble, larger than dipleg diameter, prevents the solid flow within dipleg. [ABSTRACT FROM AUTHOR]