Study On The Transformation Characteristics Of Nitrogen During Pyrolysis Of Sewage Sludge

With the wastewater discharge amount increasing, the quantity of sludge is growingquickly in China. Sludge incineration has become an efficient technology to achieve volumereduction, harmlessness and resource-oriented, but the nitrogen content in the sludge is3.3⁷.7wt%, so large amounts of nitrogen oxides （NOX） will produce during sludgecombustion. How to inhibit the formation of NOXin the sludge has become a major task,therefore, the study of nitrogen migration on the development of nitrogen emission reductiontechnology in incineration process is important.This article took three sewage sludge from Shenyang different wastewater factories asthe study object, using X-ray photoelectron spectroscopy （XPS）, meteorologicalchromatography-mass spectrometry （GC-MS） and other advanced testing methods to studynitrogen transformation of sludge in slow and fast pyrolysis process, which is of greatsignificance on the development of efficient nitrogen emission reduction technology.This paper used XPS to identify the nitrogen-containing functional groups of sludge andsemi-coke. The results indicate that the nitrogen exists in sludge in the forms of Protein-N,Pyridinic-N, Quaternary-N, Pyrrolic-N in turn, and Protein-N amounts to55%of totalnitrogen. During the reaction of pyrolysis, nitrogen oxides appeared and its proportionincreased gradually with the increase of pyrolysis temperature. During the pyrolysis reaction,Quaternary-N decomposed easily at the low temperature; with the increase of pyrolysistemperature, the decomposition rate of Pyridinic-N increased, and the decomposition rate ofPyridinic-N was less than Pyrrolic-N in the same temperature condition; and the carboncontent of the sludge were higher, the decomposition rate of Pyrrolic-N were lower.During the pyrolysis process, the yield of NH₃and HCN were increasing along with theraise of final temperature, mainly because of elevating temperature promoted the conversionof the nitrogen-containing functional group in the sludge. At500-700℃, the generated rate ofNH₃was faster, which mainly derived from the conversion of Quaternary-N and Protein-N; at400-600℃, the generated rate of HCN was faster, which mainly derived from the removal of cyan, as well as the conversion of Pyridinic-N and Pyrrolic-N. Tar-nitrogen content in thesludge is maximum at600℃, and with the raise of pyrolysis temperature, the nitrogen contentof the tar increased and then decreased. Comparing slow pyrolysis and fast pyrolysis, thecontent of tar-nitrogen were same basically, but during the fast pyrolysis the components oftar-nitrogen reduced.