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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]

• Silica alumina (Kaolin) catalyst enhances pyrolysis oil yield by 4.4% instead of gas yield reduction. • The optimum temp. for LDPE catalytic(Kaolin) pyrolysis is 520 °C lower than 560 °C at sand pyrolysis. • Light oil fractions increased to 11.9% (2.58 time more) over kaolin LDPE pyrolysis in FB reactor. • Kaolin has the potential to serve as a reliable substitute for sand. Low-density polyethylene (LDPE) is the second most prevalent waste plastic globally, followed by polypropylene. The pyrolytic conditions required to obtain light oil(≤C12) from LDPE are more stringent than those for polypropylene, water plastics, acrylonitrile, butadiene, styrene, and other materials. Consequently, numerous researchers have underscored the necessity of employing catalysts in LDPE pyrolysis. This study explored the pyrolysis characteristics of LDPE at various temperatures in a non-catalytic fluidized bed reactor. The experiments employed a mixture of sand + kaolin, one of the Si-Al catalysts, to investigate the pyrolysis of LDPE in a fluidized bed reactor at different temperatures. The findings demonstrated that using sand + kaolin as a fluidized bed material significantly enhances the yield of pyrolysis oil while concurrently reducing the gas yield compared to using sand alone. Moreover, a higher light oil fraction was obtained using kaolin (16.67 wt%) at 560 °C compared with 8.6 wt%. In addition, the study revealed that elevated temperatures (520 °C, 560 °C, and 600 °C) led to a reduction in olefins and paraffin, coupled with an increase in the formation of naphthenes, aromatics, and ketones in the pyrolysis oil. Overall, the findings underscore the promising potential of kaolin as an alternative to sand, facilitating the enhanced production of valuable light oil fractions. The insights garnered from this study are invaluable for devising effective waste management strategies. [ABSTRACT FROM AUTHOR]

CO 2 methanation, as a power-to-gas technology, is considered to be an important method to secure energy supply by utilizing CO 2 and H 2 gases. In this study, a 0.2 kW CH 4 bench-scale fluidized bed reactor was used for CO 2 methanation using approximately 13 kg nickel-based catalyst to investigate the effect of temperature, gas velocity, and H 2 /CO 2 ratio on CO 2 conversion, CH 4 purity, and CH 4 selectivity. Response surface methodology (RSM) was employed to design the experimental conditions to statistically evaluate the effect of operating variables. Reduced quadratic model equations for CO 2 conversion and CH 4 purity were derived, which determined the optimal conditions within the experimental conditions. The suggested conditions for the highest CO 2 conversion were 297 °C, 4.66H 2 /CO 2 , and 4.0 U g /U mf (velocity ratio), whereas different conditions were determined for the highest CH 4 purity. Among the operating variables, temperature was the most influential factor, followed by the gas ratio. The highest CO 2 conversion and CH 4 purity were 98% and 81.6%, respectively. Additionally, the heat transfer coefficient (h o) was found to be 115 W/m2∙°C during a 10-h continuous CO 2 methanation experiment, which is an important design factor for the further scale-up of the process. • CO 2 methanation was performed in a fluidized bed reactor using nickel beads. • CO 2 conversion and CH 4 purity were 98% and 81%, respectively. • Optimal conditions for CO 2 conversion were 297 °C, 4.6H 2 /CO 2 and 4 U g /U mf. • Heat transfer coefficient during CO 2 methanation was 115 W/m2/oC. [ABSTRACT FROM AUTHOR]