木质包装废弃物快速热解过程中的氮迁移机制

Nitrogen Transformation Mechanisms during Fast Pyrolysis of Wooden Package Waste

目的考察原料氮在木质包装材料中的分配规律。方法在固定床反应器装置上进行快速热解实验,研究胶黏剂、实木木材和刨花板在不同温度下的热解产物分布和气相产物成分分布;在热裂解气相色谱质谱联用系统上研究氮在各相产物之间,以及液相产物各组分之间的分布情况。结果原料中氮的含量和热解温度是影响氮在各相产物中分配的主要因素,且温度越高,热解气相氮产量上升,炭氮和焦油氮的含量降低;热解过程中,刨花板中氮通过自身裂解和木材组分发生交互反应生成小分子和杂环氮结构,杂环氮结构在高温下会继续裂解生成小分子,同时也会聚合生成多杂环氮结构。结论温度和施胶量是影响氮化合物成分分布的2个最主要因素。废弃刨花板中的氮来源于脲醛树脂和木材。在原料氮的裂解和聚合反应方面有2条迁移路径,一条路径会通过裂解产生氨气和炭氮,另一条路径会生成可挥发的杂环氮。

The work aims to study the distribution law of raw nitrogen in wooden packing material. Fast pyrolysis experiments were conducted on a fixed bed reactor to study distribution law of pyrolysis products and gaseous product components in adhesive, solid wood and particle board at different temperatures. Distribution law of nitrogen among products in all phases and all gaseous product components was studied by using integral pyrolysis-gas chromatography-mass spectrometry system. Nitrogen content and pyrolysis temperature were the main factors influencing nitrogen distribution among products in all phases. As the temperature increased, pyrolysis gaseous nitrogen yield increased while carbon nitrogen and tar-N decreased. During the process of pyrolysis, micromolecules and heterocyclic nitrogen structure were produced by nitorgen in particle board through self-pyrolysis and cross reaction among wood components. Heterocyclic nitrogen structure continued producing micromolecules by pyrolysis and multi-nitrogen heterocycle structure by aggregation at high temperature. In conclusion, temperature and resin consumption are the two main factors influencing composition distribution of nitrogen compounds. Nitrogen in waste particle board comes from urea formaldehyde resin and wood. And there are two transformation paths in pyrolysis and polymerization reaction of raw nitrogen. One is to produce NH3 and Char-N by pyrolysis, and the other to produce volatile heterocyclic nitrogen.