高炉炉缸区焦炭石墨化过程中多尺度孔隙结构的变化规律

Variation of multi-scale pore structure during graphitization of coke in a blast furnace hearth

在不同加热温度下(1100~1600℃)模拟高炉炉缸区焦炭的石墨化过程,利用真空排水法及氮气吸附法考察不同石墨化程度焦炭的多尺度孔隙结构演变过程。研究结果表明:二次加热后的焦炭中孔隙结构丰富且复杂,随着二次加热温度的升高,焦炭的显气孔率、比表面积、孔容积及微孔数量呈规律性变化,可分为3个过程:即1100≤t<1200,1200≤t<1400和1400≤t<1600℃,且在温度低于1400℃时灰分析出主导焦炭孔隙结构变化,大于1400℃时则主要受焦炭石墨化的影响;同时,不同石墨化程度焦炭的吸附脱附曲线均存在交叉点,且2条曲线不重合形成了"滞后环",基于滞后回线原理分析认为焦炭石墨化后的气孔结构多呈"毛囊"状;在焦炭石墨化过程中,内部灰分逐渐熔化析出至基质表面的迁移行为是导致出现上述规律的原因。

The graphitization processes of coke in the hearth of blast furnace were simulated at different heating temperatures from 1100℃to 1600℃.The evolutions of multi-scale pore structure of coke with different graphitization degrees were investigated by the vacuum drainage and nitrogen adsorption method.The results show that the pore structure of coke after reheating is abundant and complex as well.With the increase of the reheating temperature,the apparent porosity,specific surface area,pore volume and microporous quantity of coke change regularly,which can be divided into three stages,i.e.,1100≤t<1200,1200≤t<1400 and 1400≤t<1600℃.Moreover,the ash precipitation plays the leading role on the pore structure change of coke below 1400℃.Once the temperature is higher than 1400℃,the pore structure will be mainly affected by the graphitization process of coke.Besides,there are crossing points existed in the adsorption and desorption curves of coke with different graphitization degrees.The two curves do not coincide and thus forms a"hysteresis loop".Based on the principle of hysteresis loop,it can be deduced that the pore structure of graphitized coke mostly appeares as a shape of"hair follicle".It is the inner ash migration to the surface of coke substrates during the graphitization process that leads to the above law.