焦化过程半焦孔隙结构时空变化规律的实验研究——孔隙率、比表面积、孔径分布的变化

以井式加热炉(φ150mm×300mm) 为主体模拟工业炼焦过程，借助压汞法考察了焦化过程中不同焦化温度、炉内径向不同位置半焦的孔隙结构参数的变化。结果表明，半焦中存在丰富的大孔和中孔，孔隙率和比表面积随焦化温度、径向位置呈规律性变化；相同焦化温度下，由边缘沿中心方向先减少后增加；相同位置下，孔隙率随着温度的升高逐渐变小，至900℃后孔隙率略有增大，比表面积在900℃左右达到最小值后随温度升高又迅速增加；此外，半焦孔隙以孔径大于5.0μm的孔为主，孔径小于0.4μm、介于0.4μm～5.0μm和大于5.0μm的孔累积孔隙分率分别约占总孔体积分数的10％、20％和70％，孔径分布的高峰处于60 μm～150μm。SEM分析显示，焦柱中存在丰富的大孔，且边缘和中心处孔径较大。

Variation of pore structure of semi-coke with temperature and spatial location during pyrolysis——Porosity, specific surface area and pore size distribution

The pore size distribution at different temperatures and laterally spatial locations during pyrolysis was investigated by mercury intrusion method coupling with SEM analysis. A vertical furnace with the diameter of 150mm and the height of 300mm was used to simulate the coking process. The results show that there are a lot of macropore and mesopore existed in semi coke. A regular variation of porosity and specific surface area is observed with coking temperature and spatial location. At the same coking temperature, the porosity and specific surface area firstly decrease and then increase from the brim to the center of coke bed. The porosity decreases with the increase of the coking temperature, but increases after 900℃. The specific surface area reaches the minimum value at 900℃, and then rapidly increases with the increasing of temperature. The pores with the diameter of >5.0μm dominate all the pore structures. The cumulative pore volume with the pore diameter of <0.4μm、0.4μm~5.0μm and >5.0μm reaches 10 %、20 % and 70 %, respectively, and the distribution peak lies in the pore size between 60μm and 150μm. The SEM analysis results also show that the rich macropore is existed in the semi coke and the larger pore diameter is observed in the center and brim of the coke cake.