Low temperature nitrogen adsorption method was used to study on the varia-tion of pore structure of Shengli lignite in low temperature (350 ℃-600 ℃)pyrolysis process. The effects of pyrolysis temperature and de-ashing treatment on pore structure parameters inclu-ding average pore diameter,specific surface area and pore size distribution were studied.And two fractal dimensions D1and D2were calculated using the FHH(Frenkel-Halsey-Hill)method at relative pressures of 0 to 0.50 and 0.50 to 0.95,respectively.The results indicate that the spe-cific surface area and pore volume of semi-coke have the same variation trends while the specific surface area and average pore size show the opposite variation trends in the pyrolysis process. When the pyrolysis temperature is above 500 ℃,more abundant porous structure,larger specific surface area and micropore volume have been formed during the process of de-ashed lignite pyrolysis. And the number of pores with an aperture interval in 0.45 nm-1.58 nm and 2.65 nm-10.00 nm significantly increases.The results of FH H method analysis demonstrate that there are two kinds of opposite trend fractal dimensions in the semi-coke:D1and D2.Pyrolysis temperature lower than 450 ℃,D1can be used to describe the micropore surface roughness of the semi-coke which are produced by de-ashed lignite.While D2can reflect the roughness of the mesopore volume adequately in the whole pyrolysis process.%采用低温氮气吸附法分析了胜利褐煤在低温(350 ℃~600 ℃)热解过程中孔结构的变化,研究了热解温度及脱灰处理对半焦的平均孔径、比表面积和孔径分布等孔结构参数的影响,并利用FHH(Frenkel-Halsey-Hill)模型,分别在相对压力为0~0.50和0.50~0.95内计算了不同的分形维数D1和D2,用以表征煤样的分形特征.结果表明:在热解过程中,半焦的比表面积与孔容积具有相同的变化趋势,与平均孔径呈相反的变化趋势;当热解温度高于500 ℃时,脱灰褐煤转化为半焦的过程中孔结构变得更为发达,比表面积和微孔孔容明显增大,孔径区间在0.45 nm~1.58 nm及2.65 nm~10.00 nm内的孔数量明显增加;FHH 模型分析表明,半焦内存在两种变化趋势相反的分形维数D1和D2.D1可以描述450 ℃之前脱灰褐煤半焦微孔表面的粗糙程度,D2可以反映出整个热解过程中脱灰褐煤的中孔孔容粗糙程度.
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