温度和氧含量对NH_4Br改性稻壳焦汞氧化吸附特性的影响  

Effects of temperature and oxygen content on Hg^0 oxidation and adsorption by rice husk char impregnated with NH_4Br

作　　者：姚婷[1] 段钰锋[1] 朱纯[1] 周强[1] 佘敏[1] 陈亚南[1] 

机构地区：[1]东南大学能源热转换及其过程测控教育部重点实验室,江苏南京210096

出　　处：《化工学报》2016年第4期1467-1474,共8页CIESC Journal

基　　金：国家自然科学基金项目(51376046;51576044);中央高校基本科研业务费专项资金项目;江苏省普通高校研究生科研创新计划资助项目(CXZZ13_0093;KYLX_0115;KYLX_0184;KYLX15_0071);东南大学优秀博士学位论文培育基金项目(YBJJ1505);国家科技支撑计划项目(2012BAA02B01);江苏省产学研联合创新基金项目(BY2013073-10)~~

摘　　要：采用10 g·L^(-1) NH_4Br溶液对原始稻壳焦进行浸渍改性制备了脱汞吸附剂。利用比表面积及孔隙度分析仪、扫描电子显微镜/X射线能谱分析仪对改性前后稻壳焦吸附剂物理化学性质进行表征。在固定床汞吸附实验台上对吸附剂床层出口元素汞(Hg^0)和二价汞(Hg^(2+))进行同步检测,研究了不同温度下N_2气氛和N_^(2+)6.4%(体积)O_2气氛中改性稻壳焦的汞氧化吸附特性。50℃下N_2气氛、N_^(2+)6.4%(体积)O_2气氛以及150℃下N_2气氛中固定床出口均未明显检测到Hg^(2+),50℃和150℃时脱汞率均可达90%。温度为150℃时,在N_^(2+)6.4%(体积)O_2气氛中吸附剂的总汞(Hg_T)脱除效率为98.2%,其中82.2%的Hg^0被吸附脱除,其余则被O_2非均相氧化为Hg^(2+)而氧化脱除。通过对程序升温管式炉出口Hg_T进行检测研究了吸附剂表面吸附态汞的脱附特性。汞脱附峰值温度300℃表明吸附态汞可能以Hg-Br化合物的形式赋存于改性稻壳焦表面,220~350℃的脱附温度说明吸附态汞有较高的热稳定性。100.14%~118.62%的汞平衡率验证了实验结果的准确性。The mercury sorbent was prepared from raw rice husk char impregnated with 10 g·L^-1 NH4 Br solution. The physical-chemical characteristics of sorbents before and after modification were analyzed by surface area and porosity analyzer, scanning electron microscopy and X-ray energy dispersive spectroscope. The mercury oxidation and adsorption performance of the modified sorbents were investigated by analyzing mercury speciation（Hg^0 and Hg^2＋） in the outlet of a fixed bed reactor system in N2 and N^2＋6.4%（vol）O2 atmosphere at different temperatures. No obvious Hg^2＋ was detected in N2, N^2＋6.4%（vol）O2 atmosphere at 50℃ and N2 atmosphere at 150℃. Modified rice husk char exhibited a mercury removal efficiency of 90% at 50℃ and 150℃. Total mercury（HgT） removal efficiency of 98.2% was obtained in N^2＋6.4%（vol）O2 atmosphere at 150℃, 82.2% Hg^0 was bound to the sorbent surface, the remaining was removed in the form of Hg^2＋ which was generated from heterogeneous oxidation by O2 at the surface of sorbent. The heterogeneous reaction between O2 and gaseous Hg^0 at relatively elevated adsorption temperature promotes the Hg^0 oxidation efficiency of modified sorbents. Desorption performance of adsorbed mercury was identified by analyzing HgT at the outlet of temperature programmed tube furnace. Peak mercury desorption temperature of 300℃ manifested that mercury was bound to sorbent surface in the form of Hg-Br compound most likely. Mercury desorption temperature between 220℃ and 350℃ suggested high thermal stability of adsorbed mercury. Mercury balance ratio of 100.14%—118.62% verified the accuracy of experimental results in this study.

关 键 词：改性稻壳焦 脱汞 汞形态 氧化 吸附 脱附 

分 类 号：TQ534.9[化学工程—煤化学工程]