Study On Effects Of Mechanical Vibration On Needle Coke Structure Prepared By The Modiifed Coal Tar Pitch

As a kind of carbon materials with high-quality, needle coke alwaysused as raw material to produce high power (HP) and ultra high power(UHP) graphite electrode in industry area due to its small thermalexpansion coefficient, high mechanical strength, high electricalconductivity and the advantages of low energy consumption and easygraphitization. However, it was found that the needle coke produced byChina has some defects, such as large volume density, high resistivity,comparing with those from developed countries. As a fact, the importedneedle coke is a mainly part in all need coke of China at present, thatleads to a seriously restriction in the development of electric furnacesteelmaking industry in China. Therefore, how to make the preparationneedle coke with high quality true is a significant research in greatdeveloping coal chemical industry in the face of "rich coal, meager oiland little gas".Taking the D or G as a modifier for coal-tar pitch (CTP), Itsquinoline insoluble, β resin, softening point, coking value and thechanges of other physical and chemical properties were studied. The differences of modified coal tar pitch (MCTP) which obtained bydifferent mass ratio were analyzed. Compared with the unmodified RCTP,It is found that MCTP TI insoluble, β resin, softening point, coking valuewere firstly increasing after reducing, then QI insoluble increased withthe increase of the contents of modifier.Through H-NMR and elemental analysis for MCTP, theexperiments found that the hydrogen content of CTP increased, thecarbon declined content, the ratio of H/C increased after the modification.What’s more, the proportion of aromatic hydrogen increased after themodification. Fused ring structure and the degree of polymerizationwould increase after the modification. This would lead to form largeraromatic compounds and ordered structures oriented char. The chemicalstructure and heat behaviors of modified coal-tar pitch samples werecharacterized by thermogravimetry (TG), Fourier transform infraredspectrometry (FT-IR). It is shown that MCTP would produce morearomatic C-H stretching vibration absorption peak and aromatic ringframe vibration absorption peak. Aliphatic C-H stretching vibrationabsorption peak to be much weaker. MCTP had a better thermal stabilityand its best suitable amount was5%. We did a comparative analysisbetween two modifiers and speculated the possible reaction mechanism.The effects of temperature, pressure, and mechanical vibration onmesophase microspheres generated were investigated and the best carbonization process conditions were obtained. It is Believed thatincreasing pressure stimulates the growth speed of mesocarbonmicrobeads, the best preparation of mesophase temperature was425℃, aproper mechanical vibration function make a contribution to generate themesocarbon microbeads which has suitable size and homogeneousdistribution.The effect of mechanical vibration on the structure of prepared charsfrom RCTP and MCTP were investigated by polarizing microscope andX-ray diffractometer. It is thought that mechanical action produced a verysignificant impact on the semi-coke optical texture. There is a suitablevibration frequency. On the basis of mechanical vibration, fiber graindirection line has been further enhanced with the D and G modified byfurther action; The existence of mechanical and modification would makethe crystal surface distance decreases, the axial crystal ordered increasesand the graphitization degree increase.The effect of mechanical vibration on the structure of preparedneedle coke from RCTP and MCTP were investigated by polarizingmicroscope and needle coke was made a electrochemical analysis. Withthe mechanical vibration function, the structure of the needle coke had asignificant improvement and shown a ordered layered structure. With theexcessive increase of modifying agents (after more than5%), reactionsystem would occurred excessive crosslinking and this would undermine the linear structure of needle coke. The existence of mechanical andmodification would increase the electrical conductivity of needle coke.