State Key Laboratory of Environmental Criteria and Risk Assessment, Chinese Research Academy of Environmental Sciences, Beijing 100012, China; State Environmental Protection Key Laboratory of Hazardous Waste Identification and Risk Control, Chinese Research Academy of Environmental Sciences, Beijing 100012, China; College of Civil Engineering and Architecture, Liaoning University of Technology, Jinzhou 121001, China.
Key Laboratory of Photochemical Conversion and Optoelectronic Materials, Technology Institution Physical and Chemistry, Chinese Academy of Sciences, Beijing 100190, China.
Waste Manag. 2023 May 1;162:8-17. doi: 10.1016/j.wasman.2023.03.007. Epub 2023 Mar 12.
Hydrothermal carbonization (HTC) is an effective means of energizing high-water-content biomass that can be used to convert sewage sludge (SS) into hydrochar and reduce nitrogen content. To further reduce the emission of NO during the combustion of hydrochar and seek proper disposal method of liquid product, the mechanism of nitrogen conversion was studied in the range of 180-320 °C and 30-90 min. At 180-220 °C, 42.15-52.91% of the nitrogen in SS was transferred to liquid by hydrolysis of proteins and inorganic salts. At 240-280 °C, the nitrogen in hydrochar was mainly in the form of heterocyclic -N (quaternary-N, pyrrole-N, and pyridine-N). The concentration of NH-N increased from 6.82 mg/L (180 °C) to 26.58 mg/L (280 °C) due to the enhancement of the deamination reaction. At 300-320 °C, pyrrole-N (from 15.92% to 9.38%) and pyridine-N (from 5.52% to 3.73%) in the hydrochar were converted to the more stable quaternary-N (from 0.31% to 4.28%). Meanwhile, the NH-N and amino-N in the liquid decomposed into NH. Prolonging the carbonization time promoted the hydrolysis of proteins, the conversion of heterocyclic -N, and the production of NH. Under optimal reaction conditions (280 °C and 60 min), the nitrogen in the SS is converted to stable forms and the energy balance meets the requirements of circular-economy. The results show that temperature determines the nitrogen form and the carbonization time affects the nitrogen distribution. So HTC has the potential to reduce NO emissions from SS energy utilization processes.
水热碳化（HTC）是一种有效的高能化高水分生物质的方法，可以将污水污泥（SS）转化为水热炭并降低氮含量。为了进一步降低水热炭燃烧过程中 NO 的排放，并寻找液体产物的合适处置方法，研究了在 180-320°C 和 30-90min 的范围内氮转化的机制。在 180-220°C 时，SS 中 42.15-52.91%的氮通过蛋白质和无机盐的水解转化为液体。在 240-280°C 时，水热炭中的氮主要以杂环-N（季氮、吡咯-N 和吡啶-N）的形式存在。由于脱氨反应的增强，NH-N 的浓度从 180°C 时的 6.82mg/L 增加到 280°C 时的 26.58mg/L。在 300-320°C 时，水热炭中的吡咯-N（从 15.92%降至 9.38%）和吡啶-N（从 5.52%降至 3.73%）转化为更稳定的季氮（从 0.31%增至 4.28%）。同时，液体中的 NH-N 和氨基-N 分解为 NH。延长碳化时间可以促进蛋白质的水解、杂环-N 的转化以及 NH 的生成。在最佳反应条件（280°C 和 60min）下，SS 中的氮转化为稳定形式，能量平衡符合循环经济的要求。结果表明，温度决定了氮的形态，碳化时间影响了氮的分布。因此，HTC 有可能降低 SS 能源利用过程中 NO 的排放。
