| dc.description.abstract | In order to reduce the emission of carbon dioxide (CO2) to mitigate global warming, carbon capture and storage (CCS) technology plays an important role in recent years. Among of the methods for carbon dioxide capturing, pressure swing adsorption process (PSA) has obtained more attention, which is characterized by advantages such as low energy consumption, low investment, and simple operation. Based on the various selectivities of gas mixtures toward adsorbent, and according to the properties of adsorption at high pressure and desorption at low pressure, PSA uses these principles to achieve the target of gas separation.
This study utilized EIKME 13X zeolite as adsorbent with a 3-bed 9-step VPSA process to capture CO2 from pretreated flue gas exhausted by a coal-fired power plant. The CO2 concentration of pretreated flue gas is about 9.00% ~ 11.74%. To reach the goals of CO2 purity above 90% and CO2 recovery above 80%, this research chose pressure equilization / countercurrent depressurization time, adsorption / pressure equilization time and adsorption / cocurrent depressurization time of 3-bed-9-step VPSA process as the factors to set up two-level three-factor full factorial design. There were 8 experiments to be conducted. The results of experiments were used to investigate the effect of factors on CO2 purity, CO2 recovery and energy consumption of two vacuum pumps. Next, the multiple regression analysis method was utilized to build regression models of CO2 purity, CO2 recovery and energy consumption of two vacuum pumps, respectively. Finally, the regression models of CO2 purity, CO2 recovery and energy consumption of two vacuum pumps were optimized by Minitab software with CO2 purity and CO2 recovery expecting to reach above 90% and 80%, and the factors setting were estimated under this condition.
From the analyzed results, the factor adsorption / cocurrent depressurization time is the significant effect for CO2 purity; the factors pressure equilization / countercurrent depressurization time and adsorption / cocurrent depressurization time are the significant effects for CO2 recovery; there is no factor significant for energy consumption of vacuum pumps.
The results of optimizing CO2 purity, CO2 recovery and energy consumption of two vacuum pumps regression models show optimal CO2 purity 92.08%, CO2 recovery 84.32% and energy consumption of vacuum pumps 2.22 GJ/tonne CO2. Comparing with 8 experiments, the optimization results are nearly the same as the second experiment results : CO2 purity 92.01%, CO2 recovery 84.18% and energy consumption of vacuum pumps 2.20 GJ/tonne CO2. Namely, the regression models present very good predictability and accuracy. On the other hand, the factors found from optimization results are the best operating conditions of this research, and those factors are as same as the operating parameters of the second experiment. The best operating parameters are listed as the follows : pressure equilization / countercurrent depressurization time 400 seconds, adsorption / pressure equilization time 200 seconds, and adsorption / cocurrent depressurization time 90 seconds. | en_US |