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An Insight into Electrostatic Field Effects on SO3 Adsorption by CaO with CO2, SO2 and H2O: A DFT Approach

Category: Air Pollution Modeling

Volume: 19 | Issue: 10 | Pages: 2320-2330
DOI: 10.4209/aaqr.2019.04.0206
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Lu Liu1, Quanjin Deng1, Chenghang Zheng2, Shuang Wang1, Junfeng Wang 1, Xiang Gao2

  • 1 School of Energy and Power Engineering, Jiangsu University, Zhenjiang 212013, China
  • 2 State Key Laboratory of Clean Energy Utilization, Zhejiang University, Hangzhou 310027, China

Highlights

  • DFT was applied to examine the electric field dependence of SO3 adsorption on CaO.
  • Trends of the Eads in a positive or negative electric field present a great difference.
  • A positive electric field is in favor of SO3 adsorption on CaO.
  • Charge transfer of SO42– increases with the increment of adsorption energy.
  • Positive field enhances charge transfer of the surface O and Ca.

Abstract

Because of the compulsory installation of electrostatic precipitators in coal-fired power plants, SO3 and particles in flue gas inevitably pass through areas with electric field and electric charge distributed. CaO is the highest alkaline content in fly ash and has strong interactions with SO3. Therefore, it is important to understand the effects of the electric field on the binding energies of SO3 and CaO. Density functional theory calculations were applied to examine the electrostatic field dependence of SO3 adsorption on the CaO(100) surface. The energetic, geometric and electronic nature of the modeled systems was analyzed. Trends of the adsorption energy variation in a positive or negative electrostatic field presented great differences. When the electrostatic field was small, it was observed that the required adsorption energy was reduced regardless of the positive or negative electrostatic field. With increased electrostatic field strength, the adsorption energy showed an increasing trend in a positive field, while the adsorption energy decreased in a negative field. The positive field enhanced the charge density changes of the surface O across the Ca around the OCaO, while the negative field enhanced the change of the charge density of the Ca below the OCaO. The SO42–-like structure accumulated electrons as a unit and the charge transfer of the SO42– increased with the incremental adsorption energy in a linear relationship. On the H pre-adsorbed surface, the total increment was much smaller than in previous cases in a positive field, and the total variation was negligible in a negative field.

Keywords

SO3 CaO Electrostatic field Adsorption Density functional theory


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