Effect Of Minerals On Reactivity And Sulfur Content Of Coke From Pyrolysis Of High-sulfur Coking Coal Blend

Restricted by resource reserves and environmental protection,high-quality coking coal can no longer meet the increasing energy consumption,and the demand for clean and efficient utilization of high-sulfur coking coal is increasing.Due to its good coking properties,high-sulfur coal can be used to partially replace low sulfur coking coal in coal blend,which is important for reducing coal blending cost and protecting high-quality coking coal resource.The sulfur content has become an important factor restricting the ratio of high-sulfur coking coal in coal blend,the large amount of hydrogen-containing volatiles produced by the pyrolysis of high-volatile coal can be used as in-situ hydrogen to stabilize sulfur-containing free radicals and reduce the sulfur content in the coke in the process of high-sulfur coal pyrolysis.However,alkaline minerals in high-volatile coal will capture sulfur-containing free radicals,affect the sulfur removal and limit the sulfur regulation.In addition,with the gradual enlargement of blast furnaces and development of coal injection technology,the requirement for the skeleton function of metallurgical coke in blast furnace has become more stringent,which raises higher requirements for the thermal strength of coke.But the presence of alkaline minerals are catalysts for coke gasification reaction,which will cause the deterioration of the thermal properties of coke and become an important factor limiting the use of high-volatile coal in coal blending coking.Therefore,it is of great significance to reduce the trapping of sulfur by alkaline minerals and the catalytic activity of coke reactivity.In the pyrolysis process,in addition to the complex reaction of organic matter,which affects the properties of coke,the minerals in coal will also participate in the pyrolysis process and have an important impact on the coke property.Through the weakening effect of alkaline minerals in high-volatile coal to capture sulfur-containing free radicals and catalyze gasification reactions by the interaction between different species of minerals,the effective regulation of sulfur in the pyrolysis process of high-volatile coals can be achieved.The main results of this study are as below:(1)Heavy-medium sorting of high-volatile coal was conducted,the difference in the properties of components obtained under different sorting densities and effect on sulfur transformation and coke reactivity during pyrolysis of high-sulfur coking coal were investigated.Results show that the co-pyrolysis of low-density components instead of raw coal and high-sulfur coking coal can effectively increase the sulfur removal rate and reduce the reactivity of the resulting coke.Substituting MHL-1.30 components for raw coal can increase the pyrolysis sulfur removal rate from 30.85% to 34.77%,and reduce the reactivity of the resulting coke from 37.96% to 32.60%.The low-density component of the long flame coal(MHL)has low content of alkaline minerals,small structural unit and the more aliphatic side chain.The co-pyrolysis with high-sulfur coking coal can provide more active hydrogen radicals,which can stabilize the generated sulfur-containing free radicals.At the same time,the low content of minerals has a weaker ability to capture the generated sulfur-containing free radicals,which favors the significant increase of desulfurization rate.The low-density component has a lower MCI value,and the catalytic effect on coke reactivity is weak,which results in the lower coke reactivity.(2)Silicon-aluminum-based minerals(GL)were selected to blend with high-sulfur coking coal and high-volatile coal to study the effect of adding different proportions of GL on coke reactivity.The results show that the addition of GL is effective to reduce the coke reactivity,adding 0.7% of GL can reduce the reactivity of coke by about 4%.The addition of GL effectively weakens the catalytic effect of the alkaline minerals in coal on coke reactivity,and the reducing effect is more obvious when the alkaline content in high volatile coal is higher.The 10 kg coke oven experiment further confirms that the improvement effect of GL on coke reactivity is feasible in practical industrial application.(3)GL was also added with high-sulfur coal and high-volatile coal to co-pyrolysis to study the effect of GL on sulfur transformation behavior of high-sulfur coking coal.The results show that GL can not only weaken the capture of sulfur-containing free radicals by alkaline minerals,but also effectively promote the pyrolysis process,resulting in an increased release of hydrogen-containing and oxygen-containing gases,which in turn increases the release of sulfur-containing gas,and effectively improves the sulfur removal rate and reduces the sulfur content in coke,adding 0.5% GL can increase the sulfur removal rate by about9.66%.