BioDeNOx脱硝过程中N2O的产生机理及控逸研究

Nitrogen oxides are one of the major hazardous compounds to the atmosphere from industrial flue gases, which have been regarded as one control target during the "Twelfth Five-Year Plan" period with the increasing demands for the control of environmental quality. BioDeNOx is a novel and effective technology for the complete treatment of NO from flue gases since it features nitric oxide absorption by FeII(EDTA) and biological denitrification in a bioreactor. However, the current technology cannot be widely used in engineering for the nitrous oxide (N2O) emission from the BioDeNOx process. Focusing on the nitrous oxide producing, accumlating and transforming, the investigation is going to be carried out in the following aspects: It analyzes the transfer paths of nitric oxide in the bioreactor which includes chemical oxidization and biotransformation, and a dynamic model will be developed for the process and further validated by the experimental data. The effect of operating parameters such as the component of the industrial flue gases, inlet pollutant loading, temperature and pH, et al., on the nitric oxide removal efficiency and nitrous oxide accumulating and transforming ratio will be studied. It investigates the effect of electron donor on the oxidation-reduction characteristic of Fe(II)EDTA、Fe(II)EDTA-NO and Fe(III)EDTA and the effect of the complex compound form change on the nitrous oxide producing, accumlating and transforming. It confirms the transfer paths of nitrous oxide in the bioreactor which includes chemical oxidization and biotransformation. A dynamic model will be developed and further validated. The model is going to analyze the mass transfer reaction process of nitrous oxide in the bioreactor, focusing on the concentration distribution of nitrous oxide in the gas, liquid, and biofilm phases relating to the operating conditions, the major populations, the enzymes activities and microbial population change. It demonstrates the feasibility of nitric oxide removal by BioDeNOx. The results of this investigation will provide insight on the system design, configuration, and operation.

NOx是主要大气污染物之一，是国家"十二五"期间的约束性控制指标，研究和开发有效的脱硝新技术迫在眉睫。BioDeNOx集化学吸收和生物反硝化两者优点，是一项新的烟气治理新技术，本项目拟针对该体系中N2O的生成、积累和转化开展以下研究：①解析NO、N2O及主要反应产物在气、液及生物膜多相体系中的传质、反应特性和途径，建立数学模型；②获取工业烟气组分等工艺参数对NO反硝化效率及N2O生成、积累和转化的影响规律；③研究该体系中电子供体对Fe(II)EDTA、Fe(II)EDTA-NO和Fe(III)EDTA的氧化还原特性的影响，剖析络合物形态转变对N2O积累、转化过程的影响；④筛选、鉴定优势反硝化菌株，分析微群落结构，获取反硝化产物与工艺条件、优势反硝化菌株及相关酶活性、微生物种群演变之间的对应关系；⑤建立并验证BioDeNOx体系实现N2O控逸的动力学模型，为该脱硝新工艺的工程化应用奠定基础。

在BioDeNOx烟气脱硝过程中，N2O是一种主要的中间产物，研究表明N2O能够加剧温室效应，破坏臭氧层，促进酸雨的形成等。因此研究BioDeNOx脱硝体系中FeII(EDTA)-NO的生物还原及还原过程中N2O的控逸，对于实现BioDeNOx的绿色应用具有重要意义。.本研究研究了FeII(EDTA)-NO生物还原及还原过程中N2O的生成、累积和转化情况；同时分析了FeII(EDTA)-NO生物还原体系中的主要微生物及其脱氮性能，取得了以下主要研究结论：.1）经驯化后的污泥具有良好的FeII(EDTA)-NO生物还原特性，最大去除浓度为5 mmol•L-1；FeII(EDTA)-NO降解过程符合Michaels-menten方程。.2）研究FeII(EDTA)-NO还原速率发现以葡萄糖作为外加碳源时，FeII(EDTA)-NO最大还原速率Vmax达到0.77 mmol•L-1•h-1，且最适C/N为2.4；pH在弱碱性条件下，FeII(EDTA)-NO生物还原速率Vmax最大；不同温度研究比较发现，35℃有利于FeII(EDTA)-NO的生物还原。.3）以葡萄糖作为外加碳源时，FeII(EDTA)-NO生物还原过程中N2O的累积量和转化率均最低；C/N低于2.4时，易造成电子供体不足，中间产物N2O容易积累、转化率偏高；溶液pH越小，N2O累积量、转化率越高，在碱性条件下，没有检测到N2O的生成；温度在35℃下，有利于N2O的还原，温度过高、过低都会造成N2O的积累；FeIIEDTA可以作为电子供体，且浓度越高，N2O积累量越低，但相同浓度的FeIIEDTA与葡萄糖相比，葡萄糖更有利于N2O的还原。低浓度的SO32-对N2O积累和转化影响不大，较高浓度的SO32-容易造成N2O的积累。.4）BioDeNOx体系中筛选得到FeII(EDTA)-NO还原菌株HA。理化分析表明HA为革兰氏染色阴性的杆状菌，在培养基上菌落颜色为白色，菌落呈小型单个菌落，不透明，表面光滑，边缘整齐，有粘性，有芽孢，有鞭毛。其16S rDNA基因序列与厌氧芽孢杆菌属中的Anoxybacillus contaminans具有95%的相似性，综合其外部形态特征、生理生化特性以及16 S rDNA系统发育学分析，HA鉴定为厌氧芽孢杆菌(Anoxybacillus contaminans)。