Research On Solid Phase Reaction Process Based On In-situ LIBS Measurement In High Temperature Flame Field

Solid phase reaction processes are ubiquitous in the energy and chemical industries,and are often accompanied by the migration of various metal substances.In the field of clean combustion,metals not only have an impact on ash deposits in heat exchange equipment,but also a significant cause of ultra-low emission catalyst poisoning.In the field of renewable energy,molten salt acts on energy storage materials in concentrating solar power plants.At the same time,they have also attracted extensive research interest as phase change materials.However,the stability of energy storage materials in high temperature flame fields has not been widely studied.This thesis seclects energy storage materials and organic solid waste to study the solid phase reaction process in a high temperature flame field.Based on the coaxial diffusion flame burner and the Hencken multi-element diffusion flat flame burner,combined with the laser induced breakdown spectroscopy(LIBS)in-situ optical diagnostic platform are used as experimental system,the thesis studies the solid phase reaction process in the high temperature flame field of the phase change heat storage materials,municipal sludge and biogas residue.At the same time,this thesis used the simultaneous thermal analysis(STA)method to study the thermal stability of thermal storage materials,as well as the pyrolysis and combustion characteristics of municipal sludge and biogas residue.Moreover,this thesis used scanning electron microscope(SEM)and X-ray diffractometer(XRD),X-ray fluorescence spectrometer(XRF),proximate analysis,ultimate analysis,laser particle size analysis and other analytical test methods to characterize the properties of the sample.Deformation and thermal decomposition were taken place in the processes that the ceramic skeleton materials(CSM,SiO2 and MgO)based alkali metal nitrate(NaNO3 or KNO3)form-stable composite phase change material in a high-temperature flame field.The study revealed that CSM improved the thermal stability of phase change heat storage materials.Among the measured parameters,temperature has the greatest influence on nitrate decomposition.Comparing the onset temperature of decomposition and peak temperature of decomposition measured by STA and LIBS,the LIBS measurement of Na and K has the advantage of early indication.Therefore,it is of great significance in predicting the thermal stability and chemical compatibility of heat storage materials.STA of municipal sludge found that pyrolysis continued to occur throughout the heating process;the combustion process could be divided into three stages,including a water loss stage,volatiles release and burnout stage and a fixed carbon burnout stage.PS-LIBS was used to detect the characteristic atomic emission spectra of Na,Ca and A1 elements in the process of sludge combustion.By utilizing the gap between the excitation energies of the gas and particle phases,PS-LIBS was applied to distinguish the existence of metal elements in the particle or gas phase selectively along the combustion process.It was found that the content of Na element decayed first,then increased slightly and declined eventually with the three stages of combustion process,while the elements of Ca and A1 changed little.Combining coaxial diffusion flame burner with STA technology to conduct an experimental study on the combustion and pyrolysis characteristics of biogas residue.It revealed that the pyrolysis process continued throughout the temperature increase process.The combustion process could be divided into four stages,including:water loss stage,volatiles release and burnout stage,fixed carbon burnout stage and ash reaction stage.