Study On The Mechanism Of The Influence Of Sludge Lipids On The Formation Of NO_x Precursors In Protein Pyrolysis

With the rapid development of cities and industry,sludge production is also increasing.In order to reduce waste discharge,pyrolysis is an effective way to utilize energy from sludge,but the NO_x precursor（NH₃,HCN）generated in the pyrolysis process of sludge restricts the development of this technology.The NO_x precursor is mainly caused by the pyrolysis of proteins in sludge,while the organic matter in sludge mainly contains three kinds of proteins,lipids and carbohydrates.Currently,there are few studies on the mutual effect of internal components,but the mutual effect between organic matter is obvious.In this paper,based on TG-FTIR experiment and fast pyrolysis experiment in horizontal furnace,the influence mechanism of lipids on protein pyrolysis was studied.Firstly,protein in sludge were extracted by hydrolysis and lipid components in sludge were extracted by cosolvent extraction method.The effects of lipid on NH₃ and HCN were studied by TG-FTIR experiment.The main pyrolysis range of sludge protein was 150℃-600℃.Kinetic calculation showed that the activation energy of sludge protein pyrolysis was 53 k J/mol higher when lipids were added,and the lipids would make the pyrolysis of sludge protein difficult.At the same time,according to the protein and lipid structures extracted from sludge,three kinds of amino acids and palmitic acid were selected as protein and lipid compounds respectively to supplement the pyrolysis behavior analysis.FTIR results showed that NH₃production reached the peak at 300℃,decreased rapidly at 450℃,and NH₃ was disappeared at600℃.Another peak of HCN exists at 750℃.Therefore,300℃,450℃,600℃and 750℃are selected as the characteristic temperatures of pyrolysis.The simulated pyrolysis experiment results of the mold are similar to those of the actual sludge pyrolysis experiment,which provides a basis for subsequent experiments.The vertical furnace experiment was carried out with sludge protein and lipid modulates at characteristic temperature.Three phase products are collected,and we used XPS respectively,GC-MS,MS of three-phase product containing N product were analyzed,and the results show that the lipid protein for pyrolysis of solid product effect is not obvious,but for the liquid and the gas phases effect is obvious,Lipid changes in the composition of protein N-containing compound in the tar,Amino nitrogen and heterocyclic compounds were the main compounds in tar produced by protein pyrolysis alone,while amides began to appear in tar after lipids were added,The conversion effect of the three amino acids showed that palmitic acid had the most obvious effect on glutamic acid,and about 34.16%amides were generated,followed by histidine,9.17%amides,and there are only 4.25%of the tyrosine.The pyrolysis results of the gas phase showed that the palmitic acid of tyrosine inhibited the pyrolysis of glutamic acid and histidine to produce NH₃,promoted the pyrolysis of tyrosine to produce NH₃,and promoted the pyrolysis of HCN of the three amino acids at 600℃.In order to reduce the generation of NO_x precursor,the pyrolysis of sludge with high lipid content should be carried out at 600℃.This paper provides important reference value for the development of sludge pyrolysis by studying the influence mechanism of lipids on NO_x precursors for protein pyrolysis.