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不同粒度对压汞法孔隙结构测定结果的影响称为粒度效应,其可影响煤孔径分布的测定。结合粒度测试和扫描电镜观察等方法,通过开展2组无烟煤5个不同粒度系列的压汞实验,分析不同粒度孔隙结构的差异。结果显示:1随着粒度变小,总孔容增量不断增大,中—大孔的孔容和孔比表面积增量最显著,孔容和孔比表面积的展布特征由单峰态变为双峰态;2随着粒度变小,退汞率显著降低。研究认为,煤颗粒的大孔增量并非真实存在的煤中孔隙,主要为颗粒间空隙所贡献。粒度变小导致孤立形式的封闭胞腔孔和气孔得到有效释放。煤颗粒退汞结束后大部分水银仍滞留于颗粒间空隙,由此造成低退汞率的假象,煤颗粒的退汞率不能指示孔隙连通性。当煤粒径大于3mm时,基于压汞法孔隙结构的粒度效应才可忽略不计。
The effect of different particle sizes on the determination of pore structure by mercury intrusion method is called particle size effect, which can affect the determination of coal pore size distribution. Combined with particle size test and scanning electron microscope observation, the differences of pore structure at different granularities were analyzed by carrying out mercury intrusion porosimetry of 5 anthracite series with different particle sizes. The results showed that: 1 With the decrease of particle size, the increment of total pore volume increased, the pore volume and pore specific surface area increment of mesopore-macropore were the most significant. The distribution of pore volume and pore specific surface area changed from unimodal to double Kurtosis; 2 As the particle size becomes smaller, the mercury removal rate decreases significantly. The study suggests that the increase of macropores in coal particles is not a real pore in coal and mainly contributes to the intergranular void. Smaller particle sizes lead to isolated forms of closed cell pores and pores effectively released. Most of the mercury remains in the intergranular voids after the coal particles have been discharged, resulting in the illusion of low mercury removal rate. The mercury removal rate of the coal particles can not indicate the pore connectivity. When coal particle size is larger than 3mm, the particle size effect based on mercury porosimetry can be neglected.