Basic Research On Key Technologies Of Industrial Flue Gas Dry Desulfurization

China’s energy consumption pattern is mainly coal-based,and will not change in the long run,but the SO₂ produced by coal burning has great harm to the environment.Flue gas desulfurization is considered to be the most effective way to control SO₂ pollution.Dry flue gas desulfurization is achieved by the physical and chemical reaction of the adsorbent surface to achieve desulfurization,low energy consumption,simple operation method,and less corrosion to equipment,which is an economical desulfurization method.In this thesis,a new adsorbent was prepared by multi-walled carbon nanotube-loaded TiO₂（MWCNTs/TiO₂）and multi-walled carbon nanotubes doped with Cr,Cu or Zn:MWCNTs/TiO₂+Cr,MWCNTs/TiO₂+Cu and MWCNTs/TiO₂+Zn were used to remove SO₂ from simulated flue gas.The basic data were obtained by characterization and analysis of physicochemical properties of adsorbent and simulated flue gas desulfurization experiments,which provided a basis for future industrial application.MWCNTs/TiO₂ were prepared by the sol-gel method,and MWCNTs/TiO₂ were doped with Cr（NO₃）₂,Cu（NO₃）₂ and Zn（NO₃）₂ to obtain MWCNTs/TiO₂+Cr,MWCNTs/TiO₂+Cu and MWCNTs/TiO₂+Zn.On the one hand,the sorbent is used to understand the surface physicochemical properties by TEM,XRD,Raman,XPS and BET.On the another hand,in the fixed bed reactor,the experiments on the removal of SO₂ from MWCNTs/TiO₂+Cr,MWCNTs/TiO₂+Cu and MWCNTs/TiO₂+Zn were carried out.The experiment explored the fixed bed temperature,water vapor concentration and the effect of speed and metal loading on the removal of SO₂in simulated flue gas.In this paper,the dynamic adsorption processes of three kinds of samples for different concentrations of SO₂ were investigated,and the apparent adsorption kinetics,thermodynamics and equilibrium adsorption model were analyzed.The results of this research show that:（1）Compared with MWCNTs/TiO₂+Cu and MWCNTs/TiO₂+Zn,MWCNTs/TiO₂+Cr has the best desulfurization effect under the conditions of2300 ppm SO₂,8%O₂,5%H₂O,333.15 K and 1275 h^-1.The adsorption amount can reach 30.415 mg/g.（2）Controlled apparent adsorption kinetics show that the sample is affected by the absorption reaction of the outer layer during the adsorption process.Moreover,the correlation coefficient between the adsorption process of the three adsorbent and the Bangham model is high,so the Bangham model can well describe the removal process of SO₂ on the surface of the three adsorbent.The apparent adsorption kinetics of diffusion type shows that with the increase of SO₂ volume fraction and the increase of adsorption time,the prediction performance of intraparticle diffusion model is improved,and the adsorption of adsorbent is improved.The process is dominated by surface physical adsorption in the early stage of adsorption,and the reaction proceeds to the later stage in combination with diffusion and surface physicochemical reactions.（3）Adsorption thermodynamics studies show that the adsorption of SO₂by three adsorbents is a spontaneous,exothermic and entropic reduction process,and the increase in temperature is not conducive to the adsorption of SO₂ on the sample.As the volume fraction of SO₂ increases,the equilibrium adsorption capacity of the sample also increases.As the temperature increases,the equilibrium adsorption amount decreases.（4）The adsorption equilibrium data of MWCNTs/TiO₂+Cr for SO₂accords with Freundlich and Langmuir models;the adsorption process of SO₂by MWCNTs/TiO₂+Cu can be well matched with the Freundlich isotherm adsorption model,while the Langmuir model of MWCNTs/TiO₂+Zn can be well predicted.