富氧燃烧气氛下酸性气体对磁性生物焦脱汞性能影响

磁性生物焦已被证明是一种高效脱除单质汞(Hg^(0))的吸附剂。然而,SO_(2)、NO和HCl是富氧燃烧烟气中的酸性成分,其在磁性生物焦脱除Hg^(0)中的作用尚未确定。研究通过模拟富氧燃烧气氛实验装置,深入探讨了不同反应温度下酸性气体浓度对Hg^(0)吸附、氧化效率的影响,以及磁性生物焦的热再生循环性能。结果表明:120℃下,体积分数为0.4%的SO_(2)可促进磁性生物焦对Hg^(0)的吸附,脱汞率达93.5%,但较高体积分数SO_(2)(>0.4%)则产生抑制作用,且少量Hg^(0)被氧化,部分缓解SO_(2)对Hg^(0)的吸附抑制;同时,NO在富氧燃烧气氛中也表现出类似的规律;气态HCl是一种重要的促进剂,在体积分数为0.02%的HCl存在下脱汞率接近100%,可抵消烟气组分带来的不利影响。然而较高温度下,SO_(2)对磁性生物焦脱汞的作用规律与120℃时相似。350℃,体积分数为1.6%的SO_(2)对Hg^(0)吸附抑制作用更强,吸附效率只有19.5%,低于Hg^(0)氧化效率,主要生成更多的C=O等含氧官能团;NO在较高温度下也表现出较强的抑制作用,随着NO浓度增加脱汞率逐渐降低,最终降至50%左右。可见,高温、高浓度SO_(2)及NO不利于磁性生物焦脱汞。此外,脱汞后失活的磁性生物焦具有优异的热再生稳定性,在450℃下热再生并循环4次后仍有80%左右的脱汞效率。

Role of acoustic interface layer during high intensity focused ultrasound therapeutics

After interface layer was simulated by the magnetic nano-particles in the egg white phantom, high intensity focused ultrasound （HIFU） at the same dosage was introduced to radiate the phantom in different depths to blow the acoustic interface layer to mimic ＂point＂ exposure. The results showed that the volumes of biological focal region （BFR） were enlarged when the acoustic focal region （AFR） is close with interface layer. This meant that the magnetic nano-particles enhanced the therapeutic efficiency of HIFU. When the distance of the AFR from the interface layer was 10 mm, the size and shape of the BFR were similar with those of the control group, but a larger lesion at the interface, which was harmful for treatment, was observed. When the distance of the AFR to the interface layer increased to 30 mm, the size and shape of the BFR were also similar to those of the control group. When the thickness of the interface layer diminished, the utility of enhancement decreased. Continuous increase of the safe area for treatment and decrease of the utility of enhancement were observed along with the abatement of the thickness of the interface layer