模拟烟气卤素改性稻壳焦喷射脱汞试验

Experiment on mercury removal in simulated flue gas by injecting halogen modified rice husk coke

燃煤电厂是我国人为汞排放的主要来源之一,寻求合理、有效的途径来控制汞排放至关重要。目前的商用脱汞吸附剂主要来源于活性炭,开发廉价高效的生物质焦用于代替活性炭喷射脱汞具有实际意义。通过浸渍法用溴化铵溶液(NH_(4)Br)改性稻壳焦(RHC),制备溴改性稻壳焦(Br-RHC)脱汞吸附剂。通过BET表征对改性前后的脱汞吸附剂孔隙结构进行分析,在模拟烟气喷射脱汞试验装置上进行了溴改性稻壳焦吸附剂的喷射脱汞试验,考察了卤素改性、烟气温度、吸附剂停留时间、入口汞浓度以及吸附剂喷射量对喷射脱汞效率的影响。结果表明,经过卤素改性后的稻壳焦脱汞吸附剂具有丰富的孔隙结构,其比表面积、微孔容积以及总孔容积均有较大提升,Br-RHC的喷射脱汞效率是未改性RHC的3.27~3.75倍,对稻壳焦进行卤素改性可显著提高其喷射脱汞性能。提高入口汞浓度和吸附剂停留时间均可显著提高喷射脱汞效率。在入口Hg^(0)质量浓度为16.7μg/m^(3)、停留时间为2.03 s时,Hg^(0)脱除率最大;温度对喷射脱汞效率的影响呈先升高后降低的趋势,最佳温度为120℃;当吸附剂Br-RHC喷射量为7.3 g/h,Hg^(0)脱除率为70.62%;喷射量对喷射脱汞效率的影响递增并最终趋于稳定。

Coal-fired power plants are one of the main sources of anthropogenic mercury emissions in China.It is very important to find reasonable and effective ways to control mercury emissions.At present,most of the mercury adsorbents are made from activated carbon.It is actually significant to develop low cost high effective biomass cokes in place of activated carbon for mercury removal.Rice husk coke(RHC)was modified with ammonium bromide solution(NH_(4)Br)by impregnation method,and a brominated adsorbent for mercury removal from rice husk coke(Br-RHC)was prepared.The pore structure of the mercury removal adsorbent before and after modification was analyzed by BET.A test for mercury removal by injecting the Br-RHC adsorbent into a simulated flue gas duct was conducted.The effects of halogen modification,flue gas temperature,adsorbent residence time,inlet mercury concentration,and adsorbent injection amount on the mercury removal efficiency were investigated.The results show that the rice husk coke modified by halogen has an abundant pore structure than before.The BET specific surface area,microporous volume,and total pore volume are greatly improved.The injection mercury removal efficiency of Br-RHC is 3.27-3.75 times higher than that of unmodified RHC.The halogen modification of RHC can significantly improve its injection mercury removal performance.As the inlet,the Hg^(0) concentration is 16.7μg/m^(3) and the residence time is 2.03 s,the Hg^(0) removal rate reaches the maximum.The effect of flue gas temperature on injection mercury removal efficiency increases first and then decreases,and the best temperature is 120℃.When the injection mass amount of Br-RHC is 7.3 g/h,the Hg^(0) removal rate reaches 70.62%.The increase of adsorbent injection amount always promotes the efficiency of mercury removal,which finally tends to be stable.