Shu Song, Huang Yiqi, Zou Longhua, Zhang Xinyi, Li Jianjun
College of Carbon Neutrality Future Technology, Sichuan University Chengdu 610065 China
National Engineering Research Center for Flue Gas Desulfurization Chengdu 610065 China.
RSC Adv. 2023 Nov 6;13(46):32589-32595. doi: 10.1039/d3ra04672a. eCollection 2023 Oct 31.
Sodium bicarbonate (NaHCO) is considered to be an effective alkaline adsorbent for SO removal and surprisingly, the concentration of NO is significantly reduced along with the generation of NO during its desulfurization. Unfortunately, the mechanism of NO interaction with NaHCO, SO and O is ambiguous. In this work, the effects of absorption gas and absorber composition on SO/NO absorption performance were explored, the absorption products were characterized using XPS and SEM, and the Gibbs free energy of the inferred reaction path was calculated based on density functional theory (DFT). The results showed that SO and O synergistically promoted the absorption and removal of NO by NaHCO, which could completely remove SO and absorb 90% of NO at 160 °C. Sodium metabisulfite (NaSO) and sodium dithionate (NaSO) were identified as the active substances responsible for efficient NO absorption, and the oxidation of NaSO to NaSO is the controlling step of the NO removal reaction. Specifically, NaSO is an intermediate produced by the reaction of NaHCO with SO, and subsequently reacts with O to produce NaSO, which releases reactive oxygen species to oxidize NO to NO. In addition, when the S/N ratio is greater than 1 and the O content is greater than 5%, both SO and NO can maintain removal efficiency higher than 90%, indicating that the absorption reaction of SO and NO by NaHCO is highly adaptable to the flue gas composition.
碳酸氢钠（NaHCO₃）被认为是一种用于脱除SO₂的有效碱性吸附剂，令人惊讶的是，在其脱硫过程中，NO的浓度会随着NO₂的生成而显著降低。遗憾的是，NO与NaHCO₃、SO₂和O₂相互作用的机理尚不明确。在本工作中，研究了吸收气体和吸收剂组成对SO₂/NO吸收性能的影响，采用X射线光电子能谱（XPS）和扫描电子显微镜（SEM）对吸收产物进行了表征，并基于密度泛函理论（DFT）计算了推断反应路径的吉布斯自由能。结果表明，SO₂和O₂协同促进了NaHCO₃对NO的吸收和脱除，在160℃时可完全脱除SO₂并吸收90%的NO。焦亚硫酸钠（Na₂S₂O₅）和连二亚硫酸钠（Na₂S₂O₄）被确定为高效吸收NO的活性物质，Na₂S₂O₅氧化为Na₂S₂O₄是NO脱除反应的控制步骤。具体而言，Na₂S₂O₅是NaHCO₃与SO₂反应生成的中间体，随后与O₂反应生成Na₂S₂O₄，释放出活性氧将NO氧化为NO₂。此外，当S/N比大于1且O₂含量大于5%时，SO₂和NO的脱除效率均可保持高于90%，表明NaHCO₃对SO₂和NO的吸收反应对烟气组成具有高度适应性。
