配煤对气化焦孔隙结构及分形特征的影响

Effects of Blended Coal on Pore Structure and Fractal Feature of Gasification Coke

依据不同配比的焦煤、焦煤洗中煤和神木长焰煤配煤制备气化焦,利用低温氮气吸附法、压汞法和扫描电镜分析焦炭孔隙结构的变化规律,使用FHH模型在p/p0为0～0.5和0.5～0.9的相对压力下分别计算两个分形维数D_1和D_2,分析了配煤对焦炭孔隙分形特征的影响。结果表明:焦炭的微孔孔径主要分布在0.5nm～1.0nm之间,中孔孔径主要分布在2.0nm～12.0nm之间。随配煤灰分的增加,配煤灰分对焦炭孔隙的形成既有促进作用又有阻碍作用,焦炭中微孔的孔径分布呈现向孔径更大位置移动的趋势,微孔和中孔数量先增加后减少,与焦炭比表面积和孔体积变化规律一致,焦炭大孔数量先增加后略微减少;焦炭孔隙有两种分形特征D_1和D_2,D_1反映孔隙表面的粗糙度,配煤灰分增高导致更多的矿物质在高温分解成球形颗粒析出在孔隙表面,从而使得D_1增大;D_2和焦炭孔体积变化规律相似,随着配煤灰分的增高,焦炭孔隙内部复杂程度先增高后减小,D_2先增大后减小。

The gasification coke was prepared from coking coal,coking middlings and Shenmu long flame coal with different blending ratio.The change law of coke pore structure was analyzed by low temperature nitrogen adsorption method,mercury intrusion method and scanning electron microscope.Fractal dimensions D1 and D2 were calculated by using the FHH model under the relative pressures p/p 0 range of 0-0.5 and 0.5-0.9,the effects of different blended coal on the pore fractal dimension of coke were analyzed.The results show that the pore diameter of microporous is mainly distributed between 0.5 nm anD1.0 nm,and the pore diameter of mesopores is mainly distributed between 2.0 nm anD12.0 nm.With the increase of ash of blended coal,the ash of blended coal has both promoting and hindering effect on coke porosity,and the pore size distribution of micropores in coke shows a tendency to move toward a larger pore size.And the micropores and mesopores of coke increase firstly and then decrease,which are consistent with the change of coke specific surface area and pore volume.The number of macropores firstly increases and then decreases slightly.There are two fractal characteristics of coke pores D1 and D2,D1 reflects the roughness of the pore surface,and the increase of coal ash leads to more minerals decomposing into small spheres at high temperature,which causes D1 to increase.The changes in D2 are similar to micropore pore volume,indicating the volumetric roughness of micropore.As the ash of blended coal increases,D2 increases firstly and then decreases.