V2O5/AC捕获的Hg在再生过程中的释放行为研究

Release behavior of Hg captured on V2O5/AC during the regeneration process

  • 摘要: 研究了V2O5/AC捕获的Hg在再生和程序升温脱附(TPD)过程中的释放行为,考察了再生后V2O5/AC对Hg0的捕获能力。结果表明,热再生(Ar,400℃)或NH3再生(NH3/Ar,300℃)过程会使V2O5/AC捕获的大部分Hg重新释放,释放率分别为81%和94%。由于AC的还原作用,再生过程中释放的Hg以Hg0的形式为主。TPD结果表明,V2O5/AC捕获的Hg在Ar和NH3/Ar气氛下的释放行为明显不同。气氛中NH3对Hg的释放具有明显的促进作用,使Hg的释放在300℃前基本结束。但在Ar气氛下,Hg在400℃后仍有释放,致使热再生时Hg的释放率低于NH3再生时的释放率。但当NH3的体积分数由1%增加到5%时,汞的释放率变化很小。温度足够高时,两种气氛下Hg的释放率趋于一致。再生方法对V2O5/AC二次捕获Hg0的能力影响不大,两种气氛下再生后的V2O5/AC对Hg0的捕获能力差别很小,较新鲜V2O5/AC对Hg0的捕获能力有所降低,但仍高于载体AC对Hg0的捕获能力.

     

    Abstract: The release behavior of Hg captured on V2O5/AC during regeneration and temperature programmed desorption (TPD) processes was studied. The Hg0 capture capability of the regenerated V2O5/AC was also tested. It was found that 81% or 94% of Hg captured on V2O5/AC can be released during the thermal (Ar, 400℃) or NH3 (NH3/Ar, 300℃) regeneration processes. The released Hg is mainly in the form of Hg0 due to the reduction activity of carbon in AC. The TPD-AFS profile reveals that the release behavior of Hg under Ar and NH3/Ar atmospheres is different. NH3 in the atmosphere improved the release of Hg by lowering the highest release temperature to 300℃. Under pure Ar atmosphere the release of Hg still can be observed above 400℃. It caused the difference in Hg release ratio respect with the two regeneration processes tested. However, when NH3 concentration increases from 1% to 5% or higher the Hg release ratio is unchanged. If the higher regeneration temperature was used the difference in Hg release ratio during the two regeneration processes should vanish. Regeneration methods have slight effects on Hg0 capture capability on V2O5/AC. The Hg0 capture capability of regenerated V2O5/AC under the two processes is similar, which is lower than that of the fresh V2O5/AC but still much higher than that of AC.

     

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