Migration Of Metallic Elements In Group Components And Needle Coke In Coal Tar Pitch

China’s coking industry produces a large amount of coal tar pitch(CTP)every year,CTP is the main raw material for the production of graphite electrodes and new carbon materials.The quality of graphite electrode,an indispensable material in steel industry,is directly related to the production of steel in electric furnace,and the degree of CTP material purification also directly affects the properties of graphite electrode and other carbon materials.Due to the late start of the industry in China and the blockade of advanced technology by Japan and the United States,the research on CTP purification process in China is slow.Although some achievements have been made in recent years,the research on the purification and treatment of raw materials is far from enough.There are many impurities in CTP raw materials,including quinoline insoluble,S,N,metal elements,etc.Most researchers deal with quinoline insoluble in CTP.Few people pay much attention to metal impurities in CTP,which have little influence on the quality of carbon materials downstream.Therefore,this paper takes high-temperature coal tar pitch(HCTP)as raw material,separates it into four groups by cable extraction,and studies the migration and distribution of metal elements in the four groups by analyzing and determining the content of metal elements in them.The contents of 15 metal elements in HCTP and n-heptane soluble(HS),n-heptane insoluble-toluene soluble(HI-TS),toluene insoluble-quinoline soluble(TI-QS)and quinoline insoluble(QI)were determined.The results showed that the contents of Na,Ca,Fe,Mg,Zn,K,Pb and Al were more than 100 ppm,much higher than other metal elements.The contents of Ni,V,Cr,Mo,Sb,Cu and Mn all ranged from 0to 50 ppm.Na and Fe are randomly distributed in four groups of components.Al,Zn,Pb,V and Mn are mainly distributed in inorganic form in QI component.Ca,Mg,K,Ni,Cr,Mo,Sb and Cu are mainly distributed in small molecular group components such as HS and HI-TS.Taking needle coke as an example,the migration behavior of metal elements in the production process of needle coke was systematically studied by studying the changes of the content of metal elements in each stage of the production process of needle coke,and the determination and analysis of metal elements in the products of each step in the preparation process of carbon materials needle coke were carried out.The results show that most inorganic metal elements will be separated with solvent extraction and sedimentation during the pretreatment stage of raw materials.The migration rate of Na,K,Al,Mg and Pb is between 20%-40%,and that of Ca,Fe,Zn and Ni is below 10%.In the coking process,the migration rate of Na,K,Pb and Al is between 10%-25%,and that of Ca,Fe,Mg,Zn and Ni is below 10%.Less than 20% of the metal from the refined CTP to the coke is released into the gas phase.In particular,Ca remains completely in the coke in solid form due to its own non-volatile properties.In the process of high temperature calcination,the contents of Ca,K,Pb and Al change little,while Na,Fe,Mg,Zn and Ni continue to volatilize,but only less than 10% of metals are released into the gas phase,especially Zn and Ni are almost completely volatilized.The content of Na,Ca,K,Al and Pb in needle coke is relatively high,which will affect the performance of the material.This paper filled the blank of the research on metal elements in the process of needle coke production,so as to provide a certain theoretical basis for the preparation of high-performance needle coke with low metal content.