School of Environmental Science and Engineering, Huazhong University of Science and Technology, Wuhan, Hubei 430074, PR China.
School of Environmental Science and Engineering, Huazhong University of Science and Technology, Wuhan, Hubei 430074, PR China; State Key Laboratory of Coal Combustion, Huazhong University of Science and Technology, Wuhan, Hubei 430074, PR China; Hubei Provincial Engineering Laboratory of Solid Waste Treatment, Disposal and Recycling, Wuhan, Hubei 430074, PR China.
Waste Manag. 2019 Feb 15;85:452-463. doi: 10.1016/j.wasman.2019.01.014. Epub 2019 Jan 15.
The nitrogen-containing gases pyrolyzed from sewage sludge can be converted into NO compounds, which would cause severe environmental pollution. This study developed a new strategy to reduce the emission of NO precursors such as ammonia (NH) and hydrogen cyanide (HCN) using red mud. The highest reduction efficiencies (15.10% for NH and 24.72% for HCN) were achieved at 900 °C while compared with those pyrolyzed from raw sludge without the addition of red mud. The transformation and distribution of nitrogenous compounds in three-phase pyrolysates were studied at 400-800 °C for pyrolysis process of a model soybean protein compound. The nitrogenous compounds, i.e., amine-N, heterocyclic-N, and nitrile-N, were identified as the three main intermediates related with the production of NO precursors. Ferric oxide (FeO) and calcium oxide (CaO) presented in red mud were identified as the driving force which facilitated nitrogen stabilization in char (e.g., at 800 °C, 21.63% increase of char-N after addition of FeO, and 41.54% increase of char-N after addition of CaO). These metal oxides possibly reacted with protein-N to form FeN and CaCN, inhibited the secondary cracking of amine-N compounds in tar (e.g., at 800 °C, 2.33% increase of amine-N after addition of FeO, and 0.38% increase of amine-N after addition of CaO), and reduced the production of nitrile-N (e.g., at 800 °C, 30.41% reduction of nitrile-N after addition of FeO, and 27.40% reduction of nitrile-N after addition of CaO) and heterocyclic-N compounds (e.g., at 800 °C, 21.60% reduction of heterocyclic-N after addition of FeO, and 13.98% reduction of heterocyclic-N after addition of CaO). Hence, the emission of NH and HCN in gas phase can be controlled. Moreover, FeO showed better capability in controlling the emission of NO precursors than CaO (higher reduction of NH-N and higher reduction of HCN-N). These results indicate that red mud is an efficient catalyst to reduce emission of NO precursors through controlling intermediates at 400-800 °C.
从污水污泥中热解产生的含氮气体可转化为氮氧化物化合物，从而造成严重的环境污染。本研究开发了一种使用赤泥减少氨（NH）和氢氰酸（HCN）等 NO 前体排放的新策略。与未添加赤泥的原始污泥相比，在 900°C 时，NH 和 HCN 的最高还原效率分别达到 15.10%和 24.72%。在 400-800°C 下研究了模型大豆蛋白化合物热解过程中三相热解产物中含氮化合物的转化和分布。鉴定出胺-N、杂环-N 和腈-N 作为与 NO 前体生成相关的三种主要中间体。赤泥中存在的氧化铁（FeO）和氧化钙（CaO）被鉴定为促进氮在炭中稳定的驱动力（例如，添加 FeO 后炭中氮含量增加 21.63%，添加 CaO 后炭中氮含量增加 41.54%）。这些金属氧化物可能与蛋白质-N 反应形成 FeN 和 CaCN，抑制焦油中胺-N 化合物的二次裂解（例如，添加 FeO 后胺-N 增加 2.33%，添加 CaO 后胺-N 增加 0.38%），减少腈-N（例如，添加 FeO 后腈-N 减少 30.41%，添加 CaO 后腈-N 减少 27.40%）和杂环-N 化合物的生成（例如，添加 FeO 后杂环-N 减少 21.60%，添加 CaO 后杂环-N 减少 13.98%）。因此，可以控制气相中 NH 和 HCN 的排放。此外，FeO 控制 NH-N 和 HCN-N 排放的能力优于 CaO。这些结果表明，赤泥是一种通过在 400-800°C 下控制中间产物来减少 NO 前体排放的有效催化剂。
