Experiment Study And Post-treatment Design Of Molten Salt Cleaning Aiming At Paint Layer

With the worsening of resource consumption and environmental pollution,it has become the key to make manufacturing industry greener and more intelligent.As the typical form of green manufacturing,remanufacture is the inevitable choice to realize sustainable development.Remanufacturing cleaning is a key step in remanufacturing process.It costs longest time,uses most energy and effects detection and restoration.Molten salt technology is a green physical-chemical compound technology.It can decompose organics efficiently,and have achieved good application and development in dealing with hazardous wastes,medical wastes,energetic materials and other organic wastes.Molten salt cleaning is an important branch of molten salt technology,and it can alleviate the problems of efficiency and pollution in remanufacturing cleaning.In this paper,pyrolysis of paint layer in molten salt,matrix properties after cleaning and post-treatment process are studied.It provides theoretical basis for the industrial application of molten salt cleaning.Firstly,the physical and chemical properties of paint are analyzed through SEM and IR spectrum.There are N,heavy metal,aromatics and other harmful substances in paint.It is discoveried by thermogravimetric analysis that the maximum weight loss temperature of paint is 305℃ and the reaction activation energy is 74.1 kJ/mol under molten salt catalytic oxidation.It proves that molten salt has a good cleaning effect on the painted parts.After that,matrix properties of 45 steel before and after molten salt cleaning are studied.The result shows that hardness,yield strength and tensile strength are not changed basically,while surface roughness increases with the initial surface roughness after cleaning.It is found that molten salt will corrode 45 steel from microcosmic angle.The corrosion layer has loosing structure and consists of iron oxides at first.When Na and K participate in corrosion reaction,the corrosion layer gets worse.Finally,determine the component and content of tail gas by GC-MS,then analyse the chemical mechanism during molten salt cleaning.According to the physical characteristic of the tail gas,tail gas treatment scheme,in which condensation is held essential with active carbon absorption or catalytic combustion as a supplement,is proposed.Ion chromatography,total inorganic carbon analyzer,potable water quality analyzer are used to determine the content of the main components in recovered salt.After analyzing the change of salt,scheme based on the amount of OH’ per 100g is proposed to recycle and reuse salt.In addition,the corrosion layer will be removed by organic acid.At last,the process of molten salt cleaning is reformed.