Research On Modification Coking And Chemical Structure Evolution Of Xinjiang Low-quality Coking Coal In Pyrolysis Process

Coal resources are very abundant in China,but coking coal resources are relatively scarce.After more than 30 years of super-intensity mining,high-quality primary coking coal has already dried up.Xinjiang,located in the northwestern border of China,has abundant coal reserves,and variety of coking coal are complete here.However,compared with coking coal in the Mainland,coke produced from Xinjiang coking coals generally suffers from higher coke reactive index(CRI)and lower coke strength after reactive index(CSR).Therefore,it is urgent to research the modification coking behavior of coking coal in Xinjiang and its formation mechanism.In this paper,the coal constitution,structure and pyrolysis behavior of a single coking coal in Xinjiang were analyzed firstly.Secondly,the modification coking behavior of single coal and blending coal was studied experimentally,and the influence rules of coking quality under the effects of modification coking was investigated.Then,the influence of pulverized coal modifiers on the chemical structure evolution during the pyrolysis of Xinjiang coal was comparatively studied.Finally,the modification coking mechanism of Xinjiang coking coal was explained.The main conclusions of this study are as follows:(1)Based on the analysis of general industrial process properties,determination of vitrinite random reflectance,Fourier transform infrared spectroscopy,and TG analysis,the results show that the coalification degree of Xinjiang's coking coal is significantly lower than that of the same brand coal in the mainland.And for the coal molecular structure,the content of oxygen-containing functional groups is relatively high,indicating that the condensation degree of aromatic nucleus is low.(2)The pulverized coal modifier has a good effect on the modification of both single coking coal and blending coking coal in Xinjiang.During the pyrolysis process,co-carbonization of pulverized coal modifier and Xinjiang coking coal occurred,which significantly reduced CRI of coke and increased the CSR.Through the addition of pulverized coal modifiers,combining with the use of appropriate coal blending ratios for all Xinjiang coal,high-quality metallurgical coke with a CSR >60% can be obtained.(3)The pyrolysis behavior of Xinjiang fat coal was studied.The pyrolysis of fat coal leads to a decrease in the content of oxygen-containing functional groups,aliphatic side chains,etc.,and results in an increase of the aromaticity and the number of aromatic rings in the unit structure.In addition,the aromatic structures combine into larger aromatic layers,which increase the order degree,reduce the planar defects of the carbon atoms,and improve the microcrystalline structural units.(4)The pulverized coal modifier can promote the pyrolysis reaction of the low temperature section of the fat coal,which can produce more gas to penetrate the colloidal body and promote their volume expansion.In addition,the liquid phase can more easily flow and fill the gaps of the coal particles,subsequently promote the coal particles Bonding.Moreover,pulverized coal modifier can also reduce the severity of polycondensation reaction of fat coal at high temperature and reduce the production of coke cracks.In addition,the coke order degree becomes larger,the defects turn less,and the microcrystalline structural unit is further improved.