Effects Of Ni-based And Co-based Additives On Sulfur Transformation During Pyrolysis Of Coking Coal With High Sulfur

With the exploitation and utilization of coal resources,high quality coking coal resources have been increasingly scarce.Low-quality coal such as highsulfur coal is rich in coal reserve,but the high sulfur content restrains its utilization range.For the purpose of relieving demand-supply pressure of high quality coking coal resources,the use of high-sulfur coking coal resources is necessary.In order to guarantee the coke quality,the distribution behavior of sulfur during the coking process should be reasonably regulated to effectively reduce the sulfur ratio in coke.Thus,it can not only enlarge the type of coking coal,but also effectively reduce the production cost of coke.The sulfur in coal is mainly divided into inorganic sulfur and organic sulfur.Inorganic sulfur can be generally removed by flotation or other methods.The inorganic additives have effect on sulfur transformation during coal pyrolysis.Based on this,a high sulfur coal with rich organic sulfur was selected the nickel and cobalt based additives were introduced in coal by pressure impregnation to reasonably control the transformation of organic sulfur during coal pyrolysis.The temperature-programmed pyrolysis of raw coal and coal loaded additive were performed in a fixed bed to investigate the influence of inorganic additives on the sulfur transformation during coal pyrolysis,the main results obtained are shown as following:(1)Effect of nickel on the migration of sulfur during coal pyrolysis.The effect of nickel based additives on sulfur evolution during coal pyrolysis is affected by both the load pressure and the concentration of metal salt.When the concentration of metal salt is 0.1%,the release of sulfur-containing gases was inhibited during the 0.1-0.5-Ni(the coal with a nickel based metal salt concentration of 0.1% and pressure of 0.5 MPa)pyrolysis,while it was promoted during the pyrolysis of other coal samples.When the concentration of metal salt is high,the release of sulfur-containing gases was promoted by nickel during the pyrolysis process of all coal samples without the effect of loading pressure.However,when the loading pressure is 1 MPa,the sulfur content in coke is increased due to the sulfur fixation effect of nickel during coal pyrolysis.The influence of nickel on the distribution of sulfur in gas and solid phase during coal pyrolysis is different when the pressure is constant and the concentration of metal salt is different.When the load pressure is 0.1 MPa,the release of sulfurcontaining gases was promoted during coal pyrolysis without the effect of the concentration of nickel based additives,and the sulfur content in coke also decreased.When the load pressure is increased to 0.5 MPa,the release of sulfurcontaining gases was inhibited during the pyrolysis of coal with low concentration of Ni,while it was promoted with high concentration.When the pressure is 1 MPa,the release of sulfur-containing gases was promoted by Ni during coal pyrolysis process,but with the increase of Ni concentration,the promotion degrees increase first and then decrease.(2)Effect of cobalt based additives on the migration of sulfur during coal pyrolysis.The effect of cobalt based additives on the sulfur transformation during coal pyrolysis is the same with that of nickel based additives,which is affected by both the load pressure and the concentration of metal salt.When the loading concentration is low,with the increase of the load pressure,the release of sulfurcontaining gases during the pyrolysis of coal sample with cobalt based additive firstly increases and then decreases,while the sulfur content in coke showed the reverse change trend.When the loading concentration of Co is high,the sulfur content of coke decreases,but the reduction degree is different.In this case,the influence of cobalt on the sulfur distribution in gas and solid phase during coal pyrolysis is different with the increase of Co concentration.When the load pressure is 1 MPa,the loading concentration of Co is 1%,the sulfur-containing gases was inhibited by Co during coal pyrolysis,while the content of sulfur in coke was the lowest,suggesting that more sulfur were migrated to tar during coal pyrolysis.(3)The influence of two inorganic additives on sulfur content in coke was investigated.The two kinds of additives loaded with low and high metal salt concentration have the opposite effect on the sulfur reduction in coke.When the concentration of metal salt is 0.1%,the sulfur content in coal char shows a trend of decreasing firstly and then increasing with the increase of load pressure during the pyrolysis of coal samples with Ni based additives and Co based additives.The effect of Co additive on reducing sulfur content in coal char is better than that of Ni additive.When the concentration of metal salt is 2%,the sulfur content in the char of coal with Ni and Co additive increase with the loading pressure,however,the effect of Co additives on decreasing sulfur content in coal char is weaker than Ni additive.