This study reports the effects of temperature and Ca/Na acetates addition on the transformation of nitrogen during hydrothermal carbonization of sewage sludge at 160–250 °C. The nitrogen species in the hydrochar, aqueous, oil and gas products from sludge hydrothermal carbonization at different temperatures are well characterized, with a focus on the amino acid species in various products. Temperature is found to greatly affect the nitrogen transformation during sludge hydrothermal carbonization. At 160 °C, 47.3% of nitrogen is transformed into the aqueous product. When the temperature increases to 250 °C, only 27.1% of nitrogen is retained in the hydrochar, while 69.2 and 6.7% of nitrogen is present in the aqueous and oil products, respectively. During hydrothermal carbonization, the protein-N is first converted into the polypeptide-N in the aqueous product, followed by its further decomposition into the NH+ 4-N. This leads to a high content of the NH+ 4-N in the aqueous product, especially at increased temperatures. The labile protein-N is also transformed into the heterocylic-N (especially the pyrrole-N) in the hydrochar as the temperature increases. Among all nitrogen species in the aqueous product, the polypeptide-N consisting of amino acids with the alkyl group is the most stable. Moreover, the addition of NaAc and CaAc₂ reduces the nitrogen retention in the hydrochar, mainly due to enhanced hydrolysis of the protein-N. While for CaAc₂ addition, the deamination of the polypeptide-N is also enhanced, leading to a higher NH+ 4-N in the aqueous product. Our results show that the type of amino acid in protein is important to determine the nitrogen transformation pathways, and acetate addition is an important strategy for enhancing nitrogen removal in the hydrochar during hydrothermal carbonization.

这项研究报告了在160-250°C的污水污泥热液碳化过程中，温度和乙酸钙/乙酸钠的添加对氮转化的影响。污泥在不同温度下热液碳化产生的炭，水，油和气产品中的氮种类已得到很好的表征，重点是各种产品中的氨基酸种类。发现温度极大地影响了污泥水热碳化过程中的氮转化。在160°C下，有47.3％的氮转化为含水产物。当温度升至250°C时，氢炭中仅保留27.1％的氮，而水和油产品中分别存在69.2和6.7％的氮。在热液碳化过程中，首先，将蛋白质-N在水性产物中转化为多肽-N，然后将其进一步分解为NH + 4-N。这导致水性产物中NH + 4-N的含量很高，尤其是在温度升高的情况下。随着温度升高，不稳定的蛋白质-N也会在水碳中转化为杂环-N（尤其是吡咯-N）。在水性产物中所有的氮物种中，由具有烷基的氨基酸组成的多肽-N是最稳定的。此外，添加NaAc和CaAc 随着温度升高，不稳定的蛋白质-N也会在水碳中转化为杂环-N（尤其是吡咯-N）。在水性产物中所有的氮物种中，由具有烷基的氨基酸组成的多肽-N是最稳定的。此外，添加NaAc和CaAc 随着温度升高，不稳定的蛋白质-N也会在水煤中转化为杂环-N（尤其是吡咯-N）。在水性产物中所有的氮物种中，由具有烷基的氨基酸组成的多肽-N是最稳定的。此外，添加NaAc和CaAc₂减少了碳氢化合物中氮的保留，这主要是由于蛋白质N的水解增强所致。虽然对于添加CaAc ₂，但多肽-N的脱氨作用也得到增强，从而导致水性产物中的NH + 4-N更高。我们的结果表明，蛋白质中氨基酸的类型对于确定氮的转化途径很重要，而乙酸盐的添加是提高水热碳化过程中碳氢化合物中氮去除率的重要策略。