半干法脱硫灰对Hg~0的催化氧化及吸附特性

采用新型一体化脱硫工艺和循环流化床烟气脱硫工艺的脱硫灰为吸附剂,使用固定床反应器,在模拟烟气的条件下研究了两种半干法脱硫灰对汞的吸附及催化氧化特性。研究结果表明,吸附于脱硫灰表面的汞主要以Hg2+的形态存在,多数情况下,更高的汞氧化率伴随有更高的汞吸附率,HCl、Cl2、NO2在脱硫灰的催化作用下能有效氧化Hg0,且不同组分对Hg0的氧化作用可以累积,而NO和SO2抑制了脱硫灰对汞的吸附。脱硫灰中未燃尽碳和Fe2O3对脱硫灰吸附和催化氧化气态汞具有显著促进作用。汞吸附率和氧化率在使用两种脱硫灰作为吸附剂时均随温度升高先增大后减小,这是传质过程和反应速率共同作用的结果。

Adsorption and catalytic oxidation of Hg0 by semi-wet FGD ash

Adsorption and catalytic oxidation of Hg⁰  by NID(novel integrated desulfurization) ash and CFB-FGD(circulating fluidized bed flue gas desulfurization) ash were studied by exposing the adsorbent samples to a simulated flue gas stream in a fixed-bed reactor.The results showed that mercury captured on the surface of desulfurization ash was in Hg²⁺ form.Higher levels of mercury oxidation were associated with higher levels of mercury capture.Generally, higher levels of mercury oxidation and adsorption rates were achieved by exposing the adsorbent samples in the combination of any two components of Cl₂, HCl, NO₂  than in a single component.Mercury oxidation and capture rates of NID ash were higher than those of CFB-FGD ash in the same condition.Unburnt carbon and Fe₂O₃  in desulfurization ash played important roles in mercury adsorption and catalytic oxidation.Mercury oxidation and capture rates increased and then decreased with rising temperature due to the joint action of mass transfer and reaction rate.