State Key Laboratory of Pollution Control and Resource Reuse, School of Environmental Science and Engineering, Tongji University, Shanghai 200092, PR China.
State Key Laboratory of Pollution Control and Resource Reuse, School of Environmental Science and Engineering, Tongji University, Shanghai 200092, PR China.
Chemosphere. 2019 Mar;219:383-389. doi: 10.1016/j.chemosphere.2018.11.171. Epub 2018 Nov 27.
Oilfield sludge is recognized as a hazardous solid waste in China because of its considerable hydrocarbon content and other toxic components. In this study, the nitrogen transformation during pyrolysis of typical oil sludge samples produced in the Daqing oilfield (the largest oilfield in China), was experimentally investigated. X-ray photoelectron spectroscopy (XPS) and thermos gravimetric (TG) were used in laboratory-scale experiments and batch pyrolysis experiments were conducted at 200-800 °C in a tubular reactor to obtain quantitative information on the change of nitrogen conversion in the char, tar, and gas fractions. The thermal decomposition of amine-N compounds contributed to NH release below 250 °C. However, the amine-N compounds in the char were converted to amine-N and imine-N compounds in the tar, and no obvious nitrogenous gases were found when the temperature increased from 250 to 500 °C. Between 500 and 800 °C, a large amount of NH and a small portion of HCN were found owing to the secondary cracking of tar and ring opening of heterocyclic-N compounds in the char. Therefore, NH, HCN, and NO emissions can be reduced by accurate control of the pyrolysis temperature. A temperature of 400 °C was determined to be the optimal temperature for oilfield sludge pyrolysis, with 24.5% residual char and 43.0% tar produced. The results indicated that a suitable oilfield sludge pyrolysis temperature is helpful for reducing nitrogenous pollutant emissions, volume reduction, and energy recovery, which are beneficial for environmentally friendly production practices.
油田污泥在中国被认为是一种危险的固体废物，因为它含有相当数量的碳氢化合物和其他有毒成分。本研究通过实验考察了中国最大油田大庆油田产生的典型油泥样品在热解过程中的氮转化。采用 X 射线光电子能谱（XPS）和热重（TG）分析方法，在实验室规模实验和管式反应器中的批量热解实验中，在 200-800°C 下进行实验，以获得有关热解过程中 char、tar 和气体各相态中氮转化变化的定量信息。胺-N 化合物的热分解在 250°C 以下有助于 NH 的释放。然而，在 char 中存在的胺-N 化合物在 tar 中转化为胺-N 和亚胺-N 化合物，当温度从 250°C 增加到 500°C 时，没有发现明显的含氮气体。在 500-800°C 之间，由于 char 中焦油的二次裂解和杂环-N 化合物的开环，大量的 NH 和少量的 HCN 被发现。因此，通过准确控制热解温度可以减少 NH、HCN 和 NO 的排放。确定 400°C 为油田污泥热解的最佳温度，此时产生 24.5%的残余 char 和 43.0%的 tar。研究结果表明，适当的油田污泥热解温度有助于减少含氮污染物的排放、减少体积和回收能量，这有利于环保生产实践。
