Effect Of Separation Components Of High Volatile Coal On The Sulfur Transformation During Pyrolysis Of High Sulfur Coal

With the excessive exploitation of high-quality coking coal resources and increasing depth of coal mining,the relative ratio of high-sulfur coking coal increases.Since the price of high-sulfur coking coal is relatively lower due to its own characteristic and limited application,the effective utilization of high sulfur coking coal for blending coking can not only broaden the coking coal resources,but also reduce the coking cost.However,the sulfur content in coke has a strong relation with that in coal,thus increase the ratio of high-sulfur coking coal in coal blend will inevitably increase the sulfur content in coke,which further affects the production capacity of blast furnace and the quality of steel.Previous study has shown that introduce high volatile gas coal could regulate the sulfur transformation during pyrolysis by in-situ hydrogen supply,more sulfur is released with the volatiles and the sulfur content in the coke is reduced.However,it was found that different kinds of gas coals with similar volatile content have a great difference in sulfur regulation and there exist a certain limitation.Therefore,this work selected two kinds of gas coals with similar volatiles to obtain coal sample components with different vitrinite contents by heavy medium separation method.Firstly,characteristics such as coal maceral composition,pyrolysis condition and chemical structure of gas coals and their different separation components were analyzed.Then,the influence of gas coal and its separation components on the release behavior of sulfur-containing gases during the pyrolysis of high-sulfur coking coal was studied by a fixed-bed pyrolysis reactor and mass spectrometry.Combined with the analysis of sulfur content and sulfur form incoke by intelligent sulfur determination instrument and X-ray photoelectron spectroscopy（XPS）,finally,the influencing factors of directional regulation of sulfur by gas coal in the pyrolysis process of high-sulfur coking coal were comprehensively investigated,and the main conclusions are as follows:（1）The vitrinite of the two gas coals are mainly enriched in the low-density component（D1）.The vitrinite content in HCG raw coal is higher than that in LN raw coal,the vitrinite contents in HCG-D1 and LN-D1 are increased by 10.61%and 8.15%respectively.The elemental composition of each fractionated component also has obvious difference,the sulfur content decreases first and then increases with the increase of the density.Low-density fraction has higher content of hydrogen,while high-density fraction has more oxygen.The D1components of the two gas coals have more aliphatic carbon,which decompose during pyrolysis and release large amount of volatiles.With increasing separation density,aliphatic side chains decrease and aromatic structure larger than six rings increase,resulting in a a higher graphitization degree.In addition,although the types of functional groups of different fractions are similar with each other,the intensity of absorption peaks is significantly different,leading to different weight loss and weight loss rates during pyrolysis.（2）During the individual pyrolysis of gas coal and its separation components,the release temperature ranges of hydrogen-containing gases in D1 componentare both wider and the release amount are higher.The decomposition of aliphatic structure generates large amount of hydrogen-containing free radicals which favor the formation and release of H₂S,while hydrogen is mainly formed by the condensation of aromatic ring structure at high temperature and has less influence on H₂S release.Therefore,it is feasible to enrich vitrinite in high volatile coal and use the hydrogen-rich atmosphere generated in the pyrolysis process to realize in-situ hydrogen supply for the sulfur transformation during pyrolysis of high sulfur coal,but the matching of release temperature range of sulfur-containing gas and hydrogen-containing gas should be considered.（3）The D1 components of the two gas coalsimprove the quality and quantity of the plastic layer in the co-pyrolysis process,thus LL+HCG-D1 and LL+LN-D1 both have the widest plastic range,the largest maximum fluidity and maximum area,and the best thermal stability of plastic layer.The plasticity temperature region overlaps with the H₂S release temperature region in high sulfur coking coal.When the plastic interval is wider,the resistance of gas release is the least.It is conducive to the release of sulfur-containing gas and reduces the sulfur content in coke.With the blending of higher density components,the sulfur content in coke increases gradually when the plastic range of blending coal becomes narrow.Compared with the addition of HCG separation components,more alkaline minerals in LN separation components resulted in higher sulfide and sulfate content on the coke surface.Therefore,in the coking process of coal blending,on the basis of considering the regulation effect of volatiles on sulfur.In order to better guide the high volatile coal to regulate the thermal change behavior of sulfur content in high sulfur coking coal,the content of alkaline minerals of high volatile coal and the improvement effect of gas coal on the plastic range should be considered.