| With the rapid development of social economy,the ecological crisis caused by the excessive development of resources and the excessive consumption of energy is increasingly threatening human health and the sustainable development of the economy.As a major manufacturing country in the world,our country is facing more severe challenges in terms of resource consumption and waste disposal,and in the late 1990s,it opened the road of exploration and development in the field of remanufacturing.Remanufacturing engineering which has great and far-reaching significance for the development of circular economy and the construction of a conservation-oriented society is guided by full life cycle management,through the implementation of high-tech restoration of waste products(remanufactured blanks),to maximize the value of waste products,which can save 50%of the cost and 60%of energy compared with the production of new products,70%of materials and 80%reduction of pollutant emissions.As a key process in remanufacturing engineering,cleaning is significant in product quality and the smooth progress of other remanufacturing processes.Molten salt cleaning technology stands out among many cleaning technologies by virtue of its powerful and flexible cleaning ability,and it has shown great application potential in the field of remanufacturing cleaning.However,due to insufficient understanding of the surface fouling of remanufactured blanks and lacking of analysis of molten salt cleaning mechanism and theoretical guidance,it is impossible to form an efficient and environmentally friendly molten salt formula.Therefore,this paper first analyzes the characteristics of fouling pollution,establishes a mixed fouling structure model,then studies the mechanism of NaOH molten salt and mixed fouling,and uses a eutectic molten salt prediction model to adjust the ratio of NaOH-KOH to develop a model suitable for Green molten salt formula for mixed dirt removal.The main research contents are as follows:(1)The pollution characteristics of mixed fouling are analyzed from the perspective of organic-inorganic heterogeneous fouling.This paper takes carbon deposition and complex rust as the analysis object,and studies the organic structure dirt and inorganic structure dirt from the perspective of the interaction of organic-inorganic heterogeneous dirt.First,the complex component characteristics in the dirt are analyzed through multi-technology and purification-step-by-step methods,and then the structural characteristics of the mixed dirt are extracted through the dirt morphology and surface scanning structure analysis,and found that it has the characteristics of a composite structure formed by the inclusion and inclusion of organic and inorganic components.A single inorganic or organic cleaning method cannot break through this structural barrier.Finally,taking the pollution characteristics of carbon deposits and complex rust as examples,a three-dimensional structure model of organic structure dirt and inorganic structure dirt was established to provide theoretical guidance for the subsequent analysis of the removal mechanism of mixed dirt and the choice of cleaning methods.(2)Research on NaOH molten salt cleaning mechanism based on thermal analysis kinetics was taken.Due to the fast cleaning process of molten salt and the difficulty of collecting data during cleaning process,there is a lack of effective methods to study the removal effect of its removal mechanism.This paper uses the method of thermal analysis kinetics,taking slice paraffin,cetyl alcohol,and phenanthroline as the research objects,and analyzes the cleaning mechanism of NaOH molten salt for the above research objects.First,based on the chemical reaction rate equation and the Arrhenius equation,the mathematical principle and solution method of the reaction kinetics solution are analyzed.By comparing the pyrolysis curves and reaction kinetic parameters of different pyrolysis atmospheres and samples with different contents of NaOH,it is found that pyrolysis is the main action mode of the decomposition of the three substances.NaOH can promote the decomposition of alcohols and aromatic chemicals,but has no effect on the decomposition of long-chain alkanes.Then,according to the mechanism function and control mechanism,the decomposition principle of the dirt is analyzed,and it is found that the decomposition process of the dirt is a spherical symmetric phase boundary reaction,and the control mechanism is surface control.Combined with the peeling phenomenon of the dirt during the cleaning process,it is found that the molten salt ion can directly act on the organic matter wrapped by the inorganic component through penetration,causing it to decompose and gasify,and accelerate the surface dirt with the help of the reverse supporting force generated by the gasification Physical stripping.The above mechanism is named as the cleaning mechanism of molten salt organic targeting,and divided the scope for the subsequent mechanism.(3)The properties of NaOH molten salt based on the prediction model of the melting point of the eutectic molten salt was adjusted.In view of the long development cycle and high cost of current molten salt formulations,the eutectic molten salt melting point prediction model is proposed as a theoretical guide to control the properties of NaOH molten salt,and a low-temperature,green NaOH-KOH alkaline eutectic melting salt formula is developed.Through the cleaning experiment of carbon deposit,the influence of KOH content on the cleaning effect of eutectic system was explored,and it was found that adding KOH can effectively reduce the melting point of NaOH molten salt without affecting the decontamination ability of molten salt.And through experiments,it is explored that adding water to molten salt can control the viscosity of molten salt and improve the performance of molten salt at low temperatures.Finally,based on the above experiment and analysis of the influence law,a molten salt formula suitable for different cleaning needs is proposed.(4)Design a comparative test to verify the cleaning effect of eutectic molten salt.Taken complex rust as the cleaning object,through comparative experiments,comparative analysis from the three dimensions of cleaning effect,energy consumption and cleaning cost verifies the effect of eutectic molten salt and its targeting mechanism on the removal of inorganic structure dirt.The feature of "progressive" targeted cleaning mechanism of eutectic molten salt can provide space for the agglomeration and growth of inorganic components in the scale layer,loosen the structure of the rust layer,reduce the internal binding force,and make it easier to remove.Under the action of the eutectic molten salt,the cleanliness of the surface after cleaning is significantly improved,the cleaning efficiency is improved 34%,the energy consumption of the cleaning process is reduced 4.47 J for unit percentage contaminant removal,and the cleaning cost is reduced$ 0.36 also for unit percentage contaminant removal. |
PDF Full Text Request