Numerical Simulation Of Temperature Flow Field In Heating Section Of Continuous Push-boat Graphite Purification Furnace And Study Of Purification Process

High-purity graphite powder is widely used in electronics,machinery,metallurgy,national defense,aerospace,nuclear physics and other industries by virtue of its excellent electrical conductivity,wear resistance,lubricity,fire resistance,plasticity,electrical conductivity,etc.Typical applications include: Si C single crystal growth raw materials,lithium battery anode manufacturing materials,nuclear reactor internal application materials,graphite seals,etc.Although China is rich in graphite minerals,but the raw graphite has more impurities,resulting in its lower grade can not be used in the high precision industry.There are various graphite purification methods,among which chemical methods such as hydrofluoric acid method,acid-base method and chlorine baking method cannot be used in industrial production because of the shortcomings such as high corrosion of equipment,safety hazard of operation,pollution of environment and low purity of purification.The high-temperature method is mostly used in industrial production to prepare high-purity graphite powder,which has the advantages of environmental friendliness,high purity,non-toxic and noncorrosive.The purification furnace is the crucial thermal equipment in the hightemperature method,the high-temperature purification furnace in service have the disadvantages of high energy consumption,low thermal efficiency,low output and poor product consistency,thus restricting the downstream product quality and manufacturing cost.To solve these problems,a company is currently developing a new continuous push-boat graphite ultra-high-temperature purification furnace for the preparation of high-purity graphite powder,with a view to solving the above-mentioned problems.In this thesis,numerical simulations and process validation studies are carried out for this purification furnace.This paper focuses on the heating section of the above-mentioned purification furnace,and used numerical simulation to do numerical simulation of the temperature field,airflow field and eddy current heat source in the preheating section and high temperature section of the furnace chamber,in order to provide some theoretical basis for the optimization of the furnace design and subsequent graphite purification process.The main contents of the numerical simulation include: the numerical simulation of the temperature field and airflow field in the furnace chamber of the preheating section during the heating process of the purification furnace,the numerical simulation of the vortex heat source in the induction heating of the high-temperature section,the numerical simulation of the airflow field when the vessel is in the feeding chamber and the numerical simulation of the heating of the vessel in the furnace chamber of the heating section.And based on the calculation results,we analyzed and studied the influence law of gas flow rate and flow direction on the airflow and temperature field in the furnace chamber during the heating process of graphite purification furnace,the influence law of induction heating parts on the eddy current heat source and temperature field in the furnace chamber,the weight loss of graphite in the vessel and the temperature field change of the vessel at different furnace temperatures during the heating process of raw materials.Based on the simulation and optimization results,the design of the preheating section air inlet in the furnace chamber and the mechanical design of the induction heating coil in the high temperature section were optimized and modified for the graphite purification process based on the simulation and optimization results.In this paper,it is shown that the heat loss in the furnace is minimized when the air inlet speed is 10 m/s and the air inlet angle is 0° in the process design;the highest thermal efficiency and the most uniform temperature distribution in the furnace are achieved when the induction coil group spacing is 0.3 m and the coil and furnace chamber spacing is 0.4 m in the mechanical design.After the vessel enters the feeding chamber,the vessel is directly impacted by the process gas at the inlet of the vessel,and the process gas enters within the vessel with a faster airflow speed and brings the graphite powder to be purified in the vessel out of the vessel,resulting in the loss of graphite powder weight.The loss of graphite powder weight should be reduced with the reduction of the number of layers;the heating time of 40 min is enough to raise the vessel group to the specified temperature.The temperature of the two sides of the vessel facing the side with resistance heaters is higher,so the graphite powder in these two sides of the vessel is heated better and the purity is higher.After purification,scale graphite lost the most weight and petroleum coke lost the least weight;microcrystalline graphite had the best purification efficiency and petroleum coke graphite had the worst purification effect;scale graphite and petroleum coke graphite had no obvious change in shape and particle size after high temperature purification,and microcrystalline graphite had no obvious change in particle size and became loose and porous after high temperature purification.After the purification,compared with other purification furnaces,the graphite purification furnace has obvious advantages-high purification temperature,up to 3000℃;high purity of the product,up to 99.99%;high output,80～120 kg/h;low power consumption,4690 kwh;meeting the design requirements.