| Microalgae as an ideal high-nitrogen biomass,microalgae grows rapidly,and the yield and nitrogen content are very high.In recent years,hightemperature heat treatment technology has been gradually applied in the fields of microalgae treatment and preparation of biodiesel.However,in-depth research on the application of medium and low temperature hydrothermal treatment technology in microalgae energy conversion and resource application has not been carried out yet.Studies have confirmed that the key element nitrogen in the product is of great significance for the preparation of clean biooil,and the distribution and conversion of nitrogen under different hydrothermal parameters are not clear,and the adsorption characteristics of microalgal biochar as a carbon material also need to be further Research and understanding.In view of the current lack of research on the mechanism of microalgae denitrification during hydrothermal treatment,this paper carried out the following aspects of researchFirst,in this study,Spirulina platensis was used as the representative microalgae,and the effect of temperature on the distribution and evolution of nitrogen during the treatment of spirulina hydrothermal carbonization(HTC)was investigated under hydrothermal conditions.The experiment set a residence time of 30 minutes,varying temperature parameters,divided into six gradients of 180℃,200℃,220℃,240℃,260℃ and 280℃.Using the X-ray photoelectron spectroscopy(XPS)and other analytical methods to analyze the types,content,structure and morphological characteristics of nitrogencontaining functional groups in biochar at different temperatures,the chemical form and generation mechanism of nitrogen can be revealed to further study hydrothermal treatment Denitrification mechanism of microalgae and conversion mechanism of nitrogenous substances in bio-oil.The results show that the reaction temperature has a significant effect on the release and distribution of nitrogen in solid phase,water phase and bio-oil.At 180℃,increasing the HTC temperature can reduce the total nitrogen content in biochar from 43.23%to 17.47%,while the total nitrogen content in bio-oil gradually increases to about 30%.The contents of protein-N and pyridine-N in biochar decreased significantly,while the contents of pyrrole-N,quaternary-N and inorganic nitrogen increased significantly.As the temperature rises,the deamination of the protein increases and it is converted into more ammonia nitrogen.At 240℃,the inorganic nitrogen continues to change from the solid phase to the liquid phase.According to GC-MS analysis,the nitrogencontaining substances in bio-oil are mainly amine compounds generated by protein cleavage and nitrogen heterocyclic compounds generated by Maillard reaction,and continuing to increase the temperature can produce more amines and pyridines in bio-oil Compound.As the polymerization of pyrrole-N and pyridine-N increases with increasing temperature,a more stable aromatic nitrogen heterocyclic compound is produced,resulting in the concentration of nitrogen-containing substances in the liquid phase product in the hydrothermal process as organic nitrogen and inorganic Nitrogen-based.In addition,by further modifying the pyrolysis biochar of spirulina,the microwave-as sis ted modification of spirulina biochar to remove ammonia nitrogen was explored.The experimental parameters such as the dosage of biochar,microwave irradiation time and microwave temperature were changed.The results show that microwave radiation assisted biochar to remove ammonia nitrogen quickly and effectively.Furthermore,it provides a new method for microalgae energy conversion and resource utilization. |
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