Abstract
Abstract To investigate the adsorption kinetics and thermodynamic adsorption mechanism and laws of dry flue gas desulfurization, we prepared a new adsorbent by loading Cr, Cu, and Zn on TiO2-loaded multiwalled carbon nanotubes. Desulfurization experiments were also carried out. In this study, three kinds of samples were used for simulation and diffusion processes in the dynamic adsorption of different SO2 volume fractions in flue gas and thermodynamic model analysis of different temperatures in flue gas. Results show that the diffusion coefficient of SO2 in three kinds of samples ranges from 10−16 to 10−14 m2 s−1, and the diffusion may be dominated by configuration diffusion. The intraparticle diffusion model predicts that the performance improves with an increase in the SO2 volume fraction and a shift of adsorption time. This finding indicates that an increase in SO2 volume fraction and a change in adsorption time increase the Kundsen diffusion specific gravity and decrease the configuration diffusion specific gravity, thereby increasing the SO2 diffusion resistance, which becomes faster than the activation energy barrier resistance in the catalytic oxidation reaction. Thus, the diffusion resistance specific gravity increases in the total resistance of the diffusion reaction. One possible mechanism of the adsorption process is the transition to surface reaction control at the early stage of adsorption to joint control of late diffusion and surface reactions. Adsorption thermodynamics studies show that SO2 adsorption by three adsorbents is a spontaneous, exothermic, and entropic reduction process, and the increase in temperature is inconducive for SO2 adsorption in three samples.
Highlights
SO2 produced by coal combustion causes considerable harm to the environment, such as acid rain formation in water ecosystem, terrestrial ecosystem, and buildings in cities [1,2,3,4], and results in direct or indirect damage on materials and human health
The SO2 equilibrium adsorption amount corresponding to different SO2 volume fractions of three different samples in the flue gas was obtained by nonlinear fitting of dqt/dt when dqt = 0
The adsorption behavior of different SO2 volume fractions in flue gas was simulated by diffusion-controlled apparent adsorption kinetic model
Summary
SO2 produced by coal combustion causes considerable harm to the environment, such as acid rain formation in water ecosystem, terrestrial ecosystem, and buildings in cities [1,2,3,4], and results in direct or indirect damage on materials and human health. Under suitable conditions, when SO2 in the flue gas adsorbs the catalyst bed through the C-based catalyst, chemical adsorption accompanying the catalytic oxidation reaction occurs, and H2SO4 is formed and adheres to the pores of the C-based adsorption catalyst to realize SO2 removal and recover S resources during adsorbent regeneration [22,23,24]. In-depth study on the role of diffusion and surface reaction in C flue gas desulfurization and analysis of the role, laws, and mechanisms of diffusion in dynamic adsorption to provide deep insight into the physical and chemical mechanisms of adsorption is important in guiding the process of development. According to the fixed bed reaction system, the dynamic adsorption of samples in flue gas was studied, and the adsorption kinetics and thermodynamic analysis of these samples were systematically performed
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