Galbreath Kevin C, Schulz Richard L, Toman Donald L, Nyberg Carolyn M, Huggins Frank E, Huffman Gerald P, Zillioux Edward J
Energy & Environmental Research Center, University of North Dakota, Grand Forks, ND 58202-9018, USA.
J Air Waste Manag Assoc. 2005 Mar;55(3):309-18. doi: 10.1080/10473289.2005.10464626.
Representative duplicate fly ash samples were obtained from the stacks of 400- and 385-MW utility boilers (Unit A and Unit B, respectively) using a modified U.S. Environmental Protection Agency (EPA) Method 17 sampling train assembly as they burned 0.9 and 0.3 wt % S residual (No. 6 fuel) oils, respectively, during routine power plant operations. Residual oil fly ash (ROFA) samples were analyzed for Ni concentrations and speciation using inductively coupled plasma-atomic emission spectroscopy, X-ray absorption fine structure (XAFS) spectroscopy, and X-ray diffraction (XRD). ROFA deionized H2O extraction residues were also analyzed for Ni speciation using XAFS and XRD. Total Ni concentrations in the ROFAs were similar, ranging from 1.3-1.5 wt%; however, stack gas Ni concentrations in the Unit A were 0.990 microg/Nm3 compared with 0.620 microg/Nm3 for Unit B because of the greater residual oil feed rates employed at Unit A to attain higher 400-MW load conditions with a lower heating value oil. Ni speciation analysis results indicated that ROFAs from Unit A contain approximately 3 wt % NiSO4 x xH2O (where x is assumed to be 6 for calculation purposes) and appoximately 4.5 wt% of a Ni-containing spinel compound, similar in composition to (Mg,Ni)(Al,Fe)2O4. ROFAs from Unit B contain on average 2 wt% NiSO4 x 6 H20 and 1.1 wt% NiO. XAFS and XRD analyses did not detect any nickel sulfide compounds, including carcinogenic nickel subsulfide (Ni3S2) (XAFS detection limit is 5% of the total Ni concentration). In addition, XAFS measurements indicated that inorganic sulfate and organic thiophene species accounted for > 97% of the total S in the ROFAs. Unit A ROFAs contained much lower thiophene proportions because cyclone-separated ROFA reinjection is employed on this unit to collect and reburn the larger carbonaceous particles.
在常规电厂运行期间，分别从400兆瓦和385兆瓦公用事业锅炉（分别为A单元和B单元）的烟囱中获取代表性的重复飞灰样本，此时两台锅炉分别燃烧含硫量为0.9%和0.3%（质量分数）的残留油（6号燃料油）。使用经过改进的美国环境保护局（EPA）方法17采样列车组件采集样本。利用电感耦合等离子体原子发射光谱法、X射线吸收精细结构（XAFS）光谱法和X射线衍射（XRD）对残留油飞灰（ROFA）样本的镍浓度和形态进行分析。还使用XAFS和XRD对ROFA去离子水提取残渣的镍形态进行分析。ROFA中的总镍浓度相似，范围为1.3 - 1.5%（质量分数）；然而，A单元的烟囱气体镍浓度为0.990微克/立方米，而B单元为0.620微克/立方米，这是因为A单元采用了更高的残留油进料速率，以便在使用低热值油的情况下达到更高的400兆瓦负载条件。镍形态分析结果表明，A单元的ROFA含有约3%（质量分数）的NiSO₄·xH₂O（为计算方便，假设x为6）和约4.5%（质量分数）的一种含镍尖晶石化合物，其成分与(Mg,Ni)(Al,Fe)₂O₄相似。B单元的ROFA平均含有2%（质量分数）的NiSO₄·6H₂O和1.1%（质量分数）的NiO。XAFS和XRD分析未检测到任何硫化镍化合物，包括致癌的硫化亚镍（Ni₃S₂）（XAFS检测限为总镍浓度的5%）。此外，XAFS测量表明，无机硫酸盐和有机噻吩物种占ROFA中总硫的比例超过97%。A单元的ROFA中噻吩比例要低得多，因为该单元采用了旋风分离ROFA再注入技术来收集和再燃烧较大的碳质颗粒。
