【作者】 蔡灵琳；

【导师】 李伟；

【作者基本信息】 浙江大学 ， 环境工程， 2010， 硕士

【摘要】 矿物燃料燃烧排放的氮氧化物（NO_x）是导致酸雨、光化学烟雾等系列空气污染问题的重要原因之一。相关资料显示,我国近年来NO_x污染的程度和范围已相当严重。现有的烟气脱硝技术均存在投资运行成本高、产生二次污染或处理效率低等缺陷,为此,研究和开发新兴的烟气脱硝技术迫在眉睫。针对现有烟气脱硝技术的缺陷,课题组提出了化学吸收-生物还原技术来脱除烟气中的NO_x。本文作为该课题的一部分,确立了Fe（Ⅱ）Cit/Fe（Ⅱ）EDTA混合吸收体系并研究了其NO吸收特性;在选定的生物反应器内进行微生物挂膜实验;在这两部分研究基础上进行了络合吸收结合生物转化脱除NO的集成系统研究,通过优化实验,获得最优的工艺方案及其关键参数,为该技术的发展积累必要的基础数据和理论依据。确立了Cit和EDTA配比为6:1的Fe（Ⅱ）Cit/Fe（Ⅱ）EDTA混合吸收体系,该体系在保证一定的吸收效率下,减少了3/4的EDTA用量,不仅减轻了EDTA可能造成的二次污染,达到柠檬酸发酵母液废弃物资源化利用目的,而且还具有更高的经济性;NO的存在加速了Fe（Ⅱ）L的氧化速率;模拟烟气中氧气对络合剂的吸收效果有较大不利影响;Fe（Ⅱ）L吸收液适合在中性偏碱的范围内吸收NO,合理的pH值应控制在略小于7.0的范围;通过对喷淋塔内吸收NO效率考察证实了NO的吸收效率与吸收液中的Fe（Ⅱ）L浓度密切相关,随着循环吸收液中Fe（Ⅱ）L浓度下降而下降。选用PPR材料的填料塔作为生物还原反应装置,经过两个月的Enterococcussp.FR-3挂膜和一个月的Pseudomonas sp.DN-2挂膜,在进行环境电镜扫描后确认填料表面生长有一层厚实的生物膜,生物膜以短杆菌为主;O₂的存在对吸收液中Fe（Ⅲ）的还原有较大影响,是限制该法脱除NO效率的一个主要因素。化学吸收-生物还原法脱除烟气中的NO_x是切实可行的,其NO脱除率明显优于直接生物法和络合吸收法。集成系统在连续稳态运行条件下,在考察范围内,增大模拟烟气中NO浓度、O₂含量和SO₂浓度对系统NO脱除率影响不大,基本能保持在90%以上,但增大进气量会降低NO脱除率,进气量由800 mL·min^-1增加至2000 mL·min^-1时,NO脱除率从97%下降为77%。系统运行过程中柠檬酸消耗量较大,需适时添加柠檬酸。系统的生物还原负荷明显高于课题组前期的实验结果,通过进一步驯化,系统的处理负荷仍有很大的提升空间。更多还原

【Abstract】 The combustion of fossil fuels generates NO_x pollutants which cause photochemical pollution and acid rain.It is reported that the NO_x pollutants in China is seriously.Current technologies for NOx removal from flue gas have associated with some problems,such as high cost on Investment and operation,produced secondary pollutant and/or low removal efficiency.So,developing new technologies for NOx removal from flue gas is becoming an extremely urgent issue,presently.The newly proposed and adopted method in our work for NO_x removal from flue gas,i.e.chemical absorption-biological reduction integrated process,is deemed as a promising method.As a part of this work,in this paper,we established a mixture absorption system of Fe（Ⅱ）Cit and Fe（Ⅱ）EDTA,and also investigated its absorption characteristics of NO.Microbacteria proliferation experiments was carried in the selected bioreactor.Base on these two parts,we researched the chemical absorption-biological reduction integrated process.The aim of this work was to provide a new method and some fundamental data for NO_x removal from flue gas. The main experimental results were as follows:The mixture absorption system of Fe（Ⅱ）Cit and Fe（Ⅱ）EDTA was established,and the ratio of Cit and EDTA was 6:1.Using this system could reach high NO removal efficiency,and also could reduce the amount of EDTA by three quarters,which will relieved the second pollution caused by EDTA,and have better economical efficiency. NO could accelerate the oxidation reaction of Fe（Ⅱ）L.O₂ in the simulated flue gas had adverse effect,which would inhibit the NO removal efficiency.The suitable pH of absorbing solution was about 7.0.The research of NO removal efficiency in spray tower showed that removal efficiency was closely associated with the concentration of Fe（Ⅱ）L.A Packed Column madding by the material of PPR was used as bioreactor.The cultivation of Enterococcus sp.FR-3 lasted two months and the cultivation of Pseudomonas sp.DN-2 lasted one month.The formation of the biofilm on the filler was observed by ESEM（Environmental Scan Electro-Microscope）.O₂ had disadvantage effect on reduction of Fe（Ⅲ）L.It was the key factor which would inhibit the NO removal efficiency.The method of chemical absorption-biological reduction integrated process was feasible to remove NO from flue gas.Under steady-state operation,the concentration of NO,O₂ and SO₂ had no obvious inhibition on NO removal,and the removal efficiency was almost kept on above 90%.However,when the gas flow increased from 800 mL·min^-1 to 2000 mL·min^-1,the removal efficiency was decreased from 97%to 77%.Citrate would be consumed,needing supplement timely.The biological reduction load was obviously higher than our previous experiments.更多还原