| Graphite material has excellent capacity of heat resistance,electrical conductivity,thermal conductivity,chemical stability,plasticity and other characters,therefore,it is widely used in metallurgy,chemical,machinery and other fields.The traditional process for producing bulk graphite needs to roast and graphitize with petroleum coke as raw material,which cannot meet the market demand because it requires long-time procedure,high consumption,and high cost.In view of the situation of bulk graphite short supply,the workgroup puts forward a new type of continuous graphite technology by changing the mode of power supply,the way of feeding and the structure of furnace based on the traditional electric furnace and calcined ore furnace,cooperating with Liaoyang Carbon Kiln Design Institute.The new furnace type of the graphite furnace not only simplifies the production process,making a combination of roasting and graphitizing,but also has the advantages of cooling safety and continuous discharging,low power consumption to 1500 kW·h/t and so on.In order to verify the feasibility and safety of the new furnace type,the main contents of this paper are as follows:(1)Based on the theory of heat transfer and the heat dissipation characteristics of graphite furnace body,this paper realizes to simulate the optimal combination of lining with programming and application of heat transfer coefficient between furnace and environment,by using VC++ language to develop general GUI(Graphical User Interface)program.The results show that the radiation heat transfer is the main factor and the surface temperature of the furnace mainly affects the radiative heat transfer coefficient,and the radiative heat transfer coefficient is 2 times of the convective heat transfer coefficient at 200℃.The heat preservation effect of the furnace body is independent of the length of the furnace body.The best lining material of carbon black and light refractory brick thickness is all 0.35m and the structure parameters of the graphitization furnace are determined.(2)Based on the continuum hypothesis,a viscous flow model in the Euler field and fluid mechanics equations,a computational model of dynamic electrothermal coupling is established by compiling UDS(Use-Defined Scalars),UDF(Use-Defined Function),UDM(Use-Defined Memory)in Fluent.This calculation model solves the problem that the predecessors can not simulate the electrothermal coupling of flow materials,and provides theoretical reference for future scholars to solve similar problems.And the paper studys the descending behavior of petroleum coke particles in the cold model of two-dimensional graphite furnace.The experiment measures 3-10mm calcined coke particle dynamic viscosity which is 0.1 Pa s.The simulation results of the calculation model are in good agreement with the experimental data in the literature.(3)By using the calculation model established in this paper,the electrothermal coupling simulation of the flow material heated in continuous graphitization furnace is realized.The results are as follows:the independence of the numerical solution shows that the difference scheme has little effect on the simulation results.The best time step is 100s,the average size of grid cell is 0.04m.A more reasonable potential distribution can be obtained by using large cross-section electrodes.The electric field intensity on the electrode column is very small,only below 0.009V/m.The maximum temperature of furnace center can reach 2740K,fully meeting the temperature required for graphitization.The distribution of lining temperature is reasonable,meeting the use temperature of lining material.The maximum electric field intensity and current appear near the electrode,the maximum electric field intensity of the furnace is 94.8V/m,and the maximum current is 10400A.The distribution of flow field is reasonable.The simulation results of electric field temperature field and flow field can meet the basic requirements of continuous graphitization production.(4)The influence of voltage size and discharge rate on dynamic electrothermal coupling field are studied.The results show that the influence of each increase voltage on the temperature field is obvious with the decrease of discharge rate.Graphitization furnace can achieve graphitization temperature,when the discharge rate should not exceed 0.05mm/s.It is not desirable with blindly increasing the central temperature to the graphitization temperature by increasing the voltage.The temperature of the graphitization furnace can be increased more than 200-300K with the discharge rate decreased 0.005mm/s.If the temperature at most positions of the graphitization furnace is higher than 2473K,the current value in the furnace is very small.The distribution of current density is the same as the distribution of temperature,while the current and temperature reach the maximum near the electrode.Discharge rate at 0.03mm/s,voltage at 62-64V and discharge rate at 0.035mm/s,voltage at 67V production conditions is more reasonable,corresponding to the daily production of graphitization furnace are 24709kg/d and 28827kg/d. |
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