Dechlorination Performance Of Three Hydrotalcite-like Compounds In Medium-high Temperature

HC1 was generated in the municipal solid waste incineration flue gas will not only pollute the environment and,but also aggravate the migration of heavy metals and the dioxin output at mid-high temperature.so it is generally concerned by the public.In order to remove HC1 in municipal solid waste incineration flue gas for preventing its various damge. Three hydrotalcite-like compounds, i.e. Ca-HTLs, Zn-HTLs and Fe-HTLs, were prepared by co-precipitation. Then the XRD, BET and SEM are applied to characterize the physical and chemical properties of obtained samples. The results show that HTLs have obvious characteristics of layered structure with slim pore structure inside which was formed by quantities of hexagonal crystals. The specific surface area of HTLs was btween 38 and 45m2/g. The Pore size of HTLs was between 20 and 30nm.Influence of different preparation conditions on the de-chlorinating processes have been studied to obtain the optimum parameters. Result shows that HTLs got expected dechlorination efficiency when crystallization temperature of 60?, pH of 10,the composition of the material of n(M2+)/n(M3+)=3:n (Ca2+)/n(Mg2+)=2?n(Zn2+)/n(Mg2+)=2?n(Fe3+)/ n(Al3+)=2,particle size of 0.15?0.355mm? Then HTLs were used for the absorption of HC1 in a simulated flue gas under different initial concentrations of HC1, reaction temperatures, and reaction times conditions, respectively. The experiment results showed that the ideal HC1 removal efficiencies (over 86%) were achieved for all of the three hydrotalcite-like compounds under different conditions (0-360min). The removal efficiencies of HC1 first increased and then kept constant with the increase of reaction time. Meanwhile, the removal efficiencies decreased with the increasing initial concentrations of HC1 and the gas Flow rate. Moreover, with the increase of temperature from 350? to 650?, the HC1 removal efficiencies for Ca-HTLs, Zn-HTLs increased at first and then decreased while for Fe-HTLs the removal efficiency kept decreasing. Thus, the peak values of HC1 removal efficiency for Ca-HTLs, Zn-HTLs and Fe-HTLs were 97.6%,96.8% and 92.4% which were achieved at 450?,450?, and 350?, respectively. Overall, compared with Fe-HTLs, Ca-HTLs, Zn-HTLs showed better and more stable performance on the removal efficiency of HC1.Then the TG and XRD are applied to characterize the physical and chemical properties of samples at different stages. And the kinetic analysis was conducted by kinetic models, i.e. the intraparticle diffusion model. Elovich model and Bangham model.The result of TG and XRD indicates that the HC1 or Cl- replace the CO32- or OH- form a new kind of hydrotalcite-like compounds. The analysis on adsorption kinetics indicates that the adsorption process contains physical adsorption, diffusion, and chemical adsorption and the Bangham adsorption kinetics model can be used to predict the adsorption process of HC1 on the adsorbent.