Study On Mechanism Of Transformation Of N-containing Products By Sludge Pyrolysis Based On N-containing Model

According to the energy situation of China,current environmental pollution problems and the irrational status of energy utilization,using the sludge as an energy source by pyrolysis technology has attracted the attention of scholars at home and abroad.Due to the high content of protein in the sludge and the presence of nitrogen in the form of protein,nitrogen is converted into nitrogen-containing gas such as NH3,HCN and HNCO during pyrolysis,and is oxidized to NOx in the air,thereby polluting the environment.This also limits the widespread use of sludge pyrolysis technology,and it is useful to study the conversion of nitrogen during the pyrolysis process of sludge and can help promote the development of clean energy technologies.In order to study the microstructural properties of sludge,the elemental analysis of the sludge and the detection of surface functional groups are used to obtain the form of nitrogen in this paper.Based on the research conclusions of predecessors,the mechanism of nitrogen conversion in sludge is studied.Alanine anhydride is selected as a nitrogen-containing model compound.Then,TG-FTIR experiments were carried out to verify the NH3,HCN and HNCO in the pyrolysis process of nitrogen-containing model compounds,and the nitrogen conversion pathway was presumed.Finally,the Gaussian09 quantum chemistry simulation software is used to simulate the reaction path,and the formation mechanism of nitrogen-containing gas products were analyzed theoretically.In this paper,XPS(X-ray photoelectron spectroscopy)technology is used to study the main forms of nitrogen in sludge.The results show that the nitrogen in sludge mainly includes organic nitrogen and inorganic nitrogen,and organic nitrogen accounts for the largest proportion of protein.,followed by pyridinium and pyrrole nitrogen.In the pyrolysis process of alanine and alanine anhydride,the products containing nitrogen in the pyrolysis products are mainly NH3,HCN and HNCO,and the yield of NH3 is the highest.With the increase of temperature,the yield of the three products is gradually increased.When the temperature reaches 600?,the yield of the product containing nitrogen gas decreases.According to the pyrolysis products and literature data,the pyrolysis pathway is deduced.In the initial stage of the reaction,the alanine molecule forms a propane-propane dipeptide by dehydration condensation reaction,and can also generate NH3 by deamination reaction.Because the dipeptide molecule DKP has different C-N breaking modes,and the products are also different.Through the quantum chemical calculation of the pyrolysis process of nitrogen-containing model compounds,three main reaction paths and one sub-reaction path were designed.Considering the thermodynamics and kinetic analysis,the reaction pathway 1 was mainly reacted in the alanine pyrolysis process.The experimental results also indicate the main product of NH3,and HCN and HNCO are also the main nitrogen-containing products.Therefore,the simulated results based on the experimental results can be well matched with the experimental results.