| Combustion processes and its emission such as flue gas has been a long time setback to nature as well as human beings. Due to the progressive industrialization of the planet, over85%of the energy demand is supplied by fossil fuels in current. It was reported that more than98%of SO2, over90%of NOx and71%of CO2emission are generated mainly from the combustion of fossil fuels. SO2and NOx are toxin gases and directly responsible for the acid rain, photochemical smog and other atmosphere environmental problems. Moreover, CO2and NOx as two main green house gases are widely acknowledged, which pose the threaten that the global temperature will be in the range of1.4-5.8℃and sea level will rise of9-88cm by the end of this century.To avoid all these catastrophic environmental problems, many technologies such as flue gas desulfurization (FGD), selective catalytic reduction (SCR) and carbon capture and storage (CCS) have therefore been developed. However, they are often multi-step, complex, and costly. Thus attempt have been made to find a suitable method for removal SO2, NO and CO2in flue gas simultaneously. In this study, a new adsorption system was constructed. It suggested dry sorption method is one of the most attractive ways to treat the gaseous pollutants all together.The equilibrium adsorption behavior for main pollutants on candidate adsorbents were investigated and compared. The adsorption equilibrium isotherms for SO2, NO, CO2and N2on NaX and CaA zeolites were obtained at varied temperatures by a static volume instrument respectively. Henry’s law constant and selectivity were investigated to understand adsorbent and adsorbate affinity. In order to compare the shape differences among the isotherms, a new isotherm shape parameter was constructed and morphogenesis for isotherms was also discussed. Finally, Thennodynamic functions integral Gibbs’free energy, enthalpy and entropy were calculated to characterize adsorption behavior. It was found that adsorption affinity follow the order SO2>CO2>NO>N2on both zeolites. The affinity effect likely attributes to the sum of adsorbate molecular multipole moments and polarizability according to the isotherm shape and thermodynamic functions analysis. Zeolite with stronger polar surface is a more promising adsorbent candidate. Kinetics behavior was investigated using the breakthrough curve method. The overall mass transfer coefficient and diffusivity factor were determined by a linear driving force model. The results are indicative of micropore diffusion controlling mechanism. NaY zeolite has the minimum resistance of mass transfer duo to the largest pore openning. CaA zeolite exhibits the highest spatial hindered effect. NaX zeolite has good properties in both equilibrium and kinetics. Thus, it was labeled as the most potential adsorbent candidate.For improving the purification performance of candidate adsorbent NaX zeolite, ion exchange were conducted with cation K+, Ca2+, Mn2+and Co2+and so on respectively. The texture of series zeolites were examined by XRD, BET, and XPS technologies. Among the sorbents, K-NaX zeolite exhibited the best result to remove SO2, NO, and CO2all together. XPS results revealed that SO2has been oxidized to form SO42-on the solid surface, however, element N and C have never been detected. In order to understand the co-adsorption effects, pure component, binary, ternary components, and mimic flue gas breakthrough experiments were designed and carried out. It suggested that SO2and NO were bonded on the adsorbent surface with degradation of NO. A little competitive effect of CO2posed on SO? and NO adsorption system were found. Finally, monitoring of co-adsorption vending gas, thermodynamic equilibrium species simulation, TPD experiment and quantum chemical calculation technology were used to examine the interactive effect. A simple model was constructed which gives a deep understanding about the relations in the co-adsorption system. |
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