改性花生壳型煤、型焦的微观结构研究

Microstructure of Modified Peanut Shell Briquette and Formed Coke

以不同粒度的神木粉煤为原料、NaOH改性花生壳为粘结剂,在20 MPa下通过干法冷压成型制备型煤,再通过高温干馏制备型焦,并采用场发射扫描电镜、全自动比表面积及孔径分析仪对型煤、型焦的微观形貌与孔结构进行表征。结果表明,NaOH将花生壳纤维素与其表面覆盖层彻底分离,所得棒状纤维素光滑均匀,有序性强,直径约1μm。<1 mm粉煤所得型煤中粉煤粒子均匀粘连在基底平板上,并依稀可见生物质纤维丝,与煤粒镶嵌结合,共同形成型煤实体;3~1 mm粉煤所得型煤中煤粒主要以堆叠方式存在,缝隙被粘结剂浸润粘结。3~1 mm粉煤所得型焦的气孔分布较少,气孔壁厚,块度较大,机械强度较大;<1 mm粉煤所得型焦的气孔壁薄,块度小,导致焦炭抗碎强度不高。改性花生壳型焦具有Ⅲ型等温线特征,相对压力较低时发生单分子层吸附;相对压力较高时,发生多层吸附,且有毛细管凝聚现象。

Using the Shenmu pulverized coal with different particle sizes as raw materials,and NaOH modified peanut shells as binders,we prepared briquette by dry cold pressing under 20 MPa,and then prepared formed coke by high temperature distillation.Moreover,we characterized the microstructure and pore structure of briquette and formed coke by field emission scanning electron microscope and full automatic specific surface area and pore size analyzer.The results show that the cellulose of peanut shell is thoroughly separated from its surface coating by NaOH.The obtained rod-shaped cellulose is smooth and uniform with strong order,and its diameter is about 1 μm.The pulverized coal with the particle size<1 mm in briquette is evenly adhered to the base plate,and biomass fibers are dimly visible,which combine with the coal particle to form briquette entity together.The pulverized coal with the particle size of 3-1 mm in briquette mainly exists in the form of stacking,and the gaps are wetted and bonded by binder.The pore distribution of formed coke obtained from pulverized coal with the particle size of 3-1 mm is less,the pore wall is thicker,the lumpiness is larger,and the mechanical strength is larger.The pore wall of formed coke obtained from pulverized coal with the particle size<1 mm is thin and the lumpiness is small,resulting in the low crushing strength of the formed coke.The modified peanut shell formed coke has the characteristics of type Ⅲ isotherm.When the relative pressure is low,the monolayer adsorption occurs;when the relative pressure increases,the multilayer adsorption and capillary condensation occur.