在市政污水污泥微波辅助热解过程中，玉米秸秆对氮和重金属分布及迁移的影响。
Influence of corn straw on distribution and migration of nitrogen and heavy metals during microwave-assisted pyrolysis of municipal sewage sludge.
机构信息
State Key Laboratory of Organic-Inorganic Composites, College of Chemical Engineering, Beijing University of Chemical Technology, Beijing 100029, China.
State Key Laboratory of Organic-Inorganic Composites, College of Chemical Engineering, Beijing University of Chemical Technology, Beijing 100029, China.
出版信息
Sci Total Environ. 2022 Apr 1;815:152303. doi: 10.1016/j.scitotenv.2021.152303. Epub 2021 Dec 9.
This study explored pyrolysis characteristics, nitrogen transformation and migration of heavy metals during microwave-assisted pyrolysis of municipal sewage sludge in a continuously operated auger pyrolyser at different temperatures and corn straw ratios. The results showed higher temperatures and more corn straw resulted in more gas yield (e.g., CO, CO, CH and H) and less char yield. 5 wt% corn straw addition at 750 °C achieved high-quality bio-oil with less O-containing compounds, which was more favorable for upgrading to transportation fuels. Sludge chars prepared at higher corn straw ratios had lower ratios of H/C and N/C, and higher carbon content. Nitrogen transformation pathways and mechanisms were investigated. The residual ratio of heavy metals (except Cd) in sludge char was 67.74-100%. However, the residual ratio of Cd decreased significantly to 6.46% at 750 °C. Concentrations of all heavy metals in sludge char conformed to national standard (CJ/T 362-2011, China), and the potential ecological risk was slight. Sludge chars prepared in the presence of corn straw had lower ecological risk and higher retention capacity of heavy metals (e.g., Pb, Cr, Mn, Cu, Zn, and Ni) compared with pyrolysis of sewage sludge.
本研究在连续操作的螺旋式热解器中，探讨了不同温度和玉米秸秆比例下，微波辅助热解城市污水污泥过程中的热解特性、氮转化和重金属迁移。结果表明，较高的温度和更多的玉米秸秆导致更多的气体产率（如 CO、CO、CH 和 H）和更少的炭产率。在 750°C 下添加 5wt%的玉米秸秆可获得高质量的生物油，其中含氧量较低，更有利于升级为运输燃料。在较高玉米秸秆比例下制备的污泥炭具有较低的 H/C 和 N/C 比值，以及更高的碳含量。研究了氮的转化途径和机制。除 Cd 外，重金属（除 Cd 外）在污泥炭中的残留率为 67.74-100%。然而，在 750°C 时，Cd 的残留率显著下降至 6.46%。污泥炭中所有重金属的浓度均符合国家标准（CJ/T 362-2011，中国），潜在生态风险轻微。与污水污泥热解相比，在玉米秸秆存在下制备的污泥炭具有更低的生态风险和更高的重金属（如 Pb、Cr、Mn、Cu、Zn 和 Ni）保留能力。
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