Study On Pore Structure And Performance Of Carbon Anode Based On Image Analysis

With the rapid development of aluminum industry,the quality of carbon anode directly influences the anode carbon consumption,production cost,current efficiency,the purity of aluminum metal during the production of electrolytic aluminum.The pore,which usually accounts for 20%-30%of carbon anode for aluminum use,is an important part of the carbon anode.Therefore,the control of carbon anode's pore structure is one of the economic ways to improve the performance of carbon anode.However,current research work were mostly focus on the entity structure of carbon anode,while the work on pore structure is inadequate and lack of advanced analysis methods for quantitative characterization.This work is mainly based on digital image analysis technology,establishing a method for analyzing and characterizing the pore structure of carbon anode and then futher studying the relationship between pore structure parameters and performance of carbon anode.This work constructs a new analysis method of evaluating the pore structure parameters,structure property and preparing technology optimization of carbon anode for aluminium and then provides a theoretical basis to realize the pore structure's optimization control of carbon anode and the technical support for low carbon consumption in aluminum electrolytic.The main results are as follows:(1)Optimize the image analysis method of image acquisition,processing and calculation process,and combined the principle of Stereology and morphology the pore structure parameters such as pore porosity,pore diameter,shape factor,pore fractal dimension and coordination number and also the morphological paranieters of the petroleum coke particles,such as elongation,sphericity,convexity,compactness,profile and so on were defined and the related measurement analysis was realized.A quantitative characterization of carbon material,multi-angle image analysis method of statistical analysis was developed to provide technical support for the carbon material structure and performance.(2)The morphological parameters of petroleum coke particles were extracted by the method of image analysis,and the relationship between the morphological parameters of petroleum coke and the filling performance of petroleum coke was established.The results show that the density and repose angle of petroleum coke particles increase with the decreasing of petroleum coke particles.The results showed that the density and repose angle of petroleum coke particles increased with the decreasing of petroleum coke particles.Petroleum coke particle shape parameters vary with the species of petroleum coke and petroleum coke particle size,there is no obvious regularity and single shape parameter was insufficient to characterization of petroleum coke particle morphology.There is an obvious correlation between particle morphological parameter.Through principal component analysis the outline ratio,the convexity and compactness were classified to surface roughness parameters,the shape factor,the sphericity and elongation were classified to shape parameter.This process reduced the parameters and improved precision of the model.The forecasting model of petroleum coke packing density and repose angle of between predicted values and experimental values were highly consistent.(3)The open porosity of coke particles was measured by image analysis method According to the change of density of petroleum coke particles before and after kneading,a method for measuring the amount of the hole in the pitch of petroleum coke was put forward.The results showed that the total porosity of the petroleum coke particles and open porosity decreases with the decrease of petroleum coke particles;petroleum coke pore opening asphalt absorption coefficient decreases with the decrease of petroleum coke particles,and increases with the increase of the mixing time and mixing temperature increase pinch try,increase the amount of asphalt added first and then increase gradually stable.Carbon anode green density increases with the increase of petroleum coke pore opening Asphalt Absorption coefficient.At the same time,the density of petroleum coke increases with the increase of the amount of asphalt absorption.Green preparation should be based on the changes of petroleum coke pore opening Asphalt Absorption Coefficient even adjusting the process parameters to achieve the purpose of producing high quality anode process.(4)Through the image analysis method and the gray theory,the relationship between the pore characteristics and the resistivity of the carbon anode is studied.The results show that the pore distribution in the carbon anode satisfies the fractal law,and the larger the dimension is,the more complex the pore distribution is.The carbon anode resistivity increases with the increase of the porosity of the carbon anode.The resistivity of the carbon anode is affected by the porosity and the distribution of pores.By grey correlation theory to analyze correlation between pore size distribution and resistivity,the resistivity and the diameter of carbon anode in 100-200um pores between the maximum degree,mainly control the pore structure and reduce the range of pore size distribution inhomogeneity will help reduce the carbon anode resistivity.(5)Using image analysis method to study the change of pore structure parameters in carbon anode oxidation process.The results show that under the condition of 28MPa prepared by anode weight loss was lowest,the weight loss rate of 36MPa under the conditions of the preparation of anode reaction,the initial anode loss rate increased significantly,but with the increasing of reaction rate tends to be stable,the sample weight loss rate difference decreases gradually,and tends to be stable.Along with the increasing of reaction time inside the anode porosity increases;the pore number decreased first and then increased;the pore shape parameter,pore and micro cracks become narrow;pores are constantly increasing;anodic oxidation of the apparent activation energy decreases.Based on the change inside the anode of petroleum coke and pitch coke porosity that pitch coke and petroleum coke internal diffusion activation energy difference is the preferred asphalt selective oxidation,anode to generate the dregs of the real reason.