Study On The Influence Of Waste Plastics On The Carbon Structure Of Coke

It is well known that coke in the blast furnace must possess optimal thermal strength and low reactivity to maintain desirable permeability.Due to the limited resources of high-quality coking coal in China,the use of high-quality coking coal can be reduced by expanding coal blending resources to the coals otherwise are not suitable to produce metallurgical coke.Waste plastic is a kind of complex high molecular-weight hydrocarbon polymer,which current disposal methods are environmentally problematic.Adding a certain amount of waste plastics into the coal blends has attracted significant attention in the coke-making industry at home and abroad.The complex chemical reaction of waste plastics with coal during coke-making process may have a significant impact on the carbon structure of coke,thus impacting the properties of the coke.Xiaoxian fat coal and Qinglongshan coking coal,polyethylene and polystyrene waste plastics were used in this study.Waste plastic was first added to the coal at various ratios and then its coked to determine the thermal properties of the respective coke and analyze the carbon structure,so as to provide a theoretical basis for the application of waste plastics in coal blending coking.（1）This study showed that the pyrolysis rate of waste plastics is much higher than that of coking coal,and the temperature range at which waste plastic decomposes overlaps with that of coal,allowing for the interaction to take place.Compared with polystyrene,the synergistic effect of polyethylene and coking coal is more significant.The thermal properties of each coke sample were analyzed from two aspects of the types and ratios of waste plastics.The results showed that compared with raw coal coke,when the proportion of waste plastics is less than 4%,the thermal performance of coke is improved and the coke quality is improved.（2）The microcrystalline structure of coke was analyzed by X-ray diffractometer and High-Resolution Transmission Electron Microscope.The results indicated that with the addition of waste plastic,the length,stacking height,bending degree,and interlayer spacing of carbon microcrystalline were affected to some extent.When the proportion of waste plastics is 2%,the crystallite size of coke sample is the largest;the basic coke sample of Qinglongshan coking coal has less disordered structure and higher graphitization degree than that of Xiaoxian fat coal.Raman spectrum analysis shows that when the proportion of waste plastics is 2%,the ratio of D₁and G bands is the smallest,indicating higher degree of order.However,with the increase of the proportion of waste plastics,the ratio of D₁and G bands increased gradually,and the degree of coke disorder deepens again;it was observed in the X-ray photoelectron spectroscopy analysis that the carbon atom bonding mode of coke changed after adding waste plastics.Graphitic carbon and aliphatic carbon were the main components in the coke sample,which had a certain impact on the degree of aromatic ring condensation and alkyl side chain of the coke sample.（3）The carbon structure of the coke was found to have a profound impact on the coke CO₂reactivity and post reaction strength.Coal rank played a significant role in the correlation between coke thermal properties and carbon structure parameters.