Study On Key Technology And Device Of On-site Measurement Of Primary Crystallization Temperature Of Aluminum Electrolyte

Modern aluminum industry adopts cryolite alumina molten salt electrolysis,which is the only method to smelt aluminum in industry.The primary crystallization temperature of aluminum electrolyte is the key parameter of production process control in aluminum electrolysis.Particularly,the aluminum electrolysis temperature and superheat must be set by the primary crystallization temperature of aluminum electrolyte.Low temperature aluminum electrolysis can significantly reduce energy consumption.To realize low temperature aluminum electrolysis,researchers often add fluorine salt and other additives to the electrolyte system.The addition of additives makes the aluminum electrolyte system more and more complex.At present,the method of off-line measurement of primary crystal temperature by step cooling curve commonly used by aluminum electrolysis production enterprises has some problems,such as unclear temperature inflection point,insufficient accuracy and lagging results,which can not meet the requirements of enterprise technology upgrading,digital aluminum electrolytic cell and fine control.Based on the needs of technological upgrading and fine control of aluminum electrolysis industry,it is urgent to develop on-site measurement technology and device of aluminum electrolyte primary crystal temperature suitable for the requirements of high temperature,strong magnetic field and strong corrosion in aluminum electrolysis industry.Combined with the on-site environment and data acquisition requirements of aluminum electrolysis production,this paper mainly carries out the following research work:1.Design and complete the temperature signal acquisition and conversion circuit.High temperature molten aluminum electrolyte is highly corrosive.In this study,the armored thermocouple with corrosion resistance and high temperature resistance is selected as the temperature sensing unit,the high-efficiency analog-to-digital converter is used for analog-to-digital signal conversion,the low-cost Arduino single chip microcomputer is used for data processing,and the USB communication module is used for data transmission,analysis and storage with PC.2.The algorithm model of primary crystal temperature suitable for different electrolyte systems is established.According to the characteristics of step cooling curves of primary crystallization temperature of different electrolyte systems,an algorithm suitable for calculating primary crystallization temperature of different electrolyte systems,temperature density algorithm,is proposed.The problem that the primary crystal temperature of different electrolyte systems cannot be calculated uniformly is solved.3.Based on the finite element thermal field analysis,the on-site sampling device and sampling scheme of molten aluminum electrolyte are designed.The aluminum electrolysis production site is in a harsh environment with high temperature,strong magnetic field and strong corrosion.The sampling device shall consider its high temperature resistance,corrosion resistance and magnetic field resistance.According to the requirements of field environment,ANSYS software is used for auxiliary design,and the thermal field of samplers with different materials,shapes and sizes is analyzed.The distribution law of molten aluminum electrolyte temperature field in the sampler is obtained,which provides a reliable basis for molten aluminum electrolyte field sampling device and sampling scheme.