SO₃ Removal from Flue Gas by Using Na₂SO₃
2020
He, Kejia | Song, Qiang | Yan, Zhennan | Yao, Qiang
SO₃ emissions from coal-fired plants cause equipment corrosion and environmental pollution, which can be alleviated by adsorbent injection. The dynamic adsorption of SO₃ by Na₂SO₃ was studied with a fixed-bed reactor at 250–350 °C under simulated flue gas. An obvious competitive reaction of Na₂SO₃ oxidation by O₂ was found during SO₃ adsorption. The conversions of Na₂SO₃ by SO₃ adsorption and by O₂ oxidation all rapidly increased in the initial stage and then slowly increased. The selectivity of SO₃ adsorption by Na₂SO₃ also rapidly increased first and then slowly increased, except at 250 °C. It was between 0.06 and 0.12 in the later stage. Decreasing temperature and increasing SO₃ concentration increased the SO₃ selectivity. Na₂SO₃ oxidation was also promoted by the increasing SO₃ concentration. Pore structure analysis showed that a more porous product layer was formed by the enhanced SO₃ adsorption, facilitating the O₂ diffusion. As the product gas of SO₃ adsorption, the presence of SO₂ in the reactant gas suppressed the forward reaction of Na₂SO₃ and SO₃. Thus, increasing SO₂ concentrations weakened SO₃ adsorption and decreased the SO₃ selectivity. The strong competitive reactions greatly reduced the effective utilization of adsorbents, which should be considered during deSO₃ process design.
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