不同干燥方式下叶丝孔隙结构的变化特征

Variation of Pore Structure in Cut Strips Dried by Different Drying Means

为了探明不同干燥方式下叶丝孔隙结构的变化规律,采用实验室滚筒和下行床干燥装置,考察了烤烟和白肋烟叶丝干燥过程中内孔容积、叶丝体积、孔径分布及孔隙形貌的变化特征。结果表明：1不同干燥方式下叶丝内孔容积均存在明显的收缩,且烤烟叶丝内孔容积收缩程度高于白肋烟;在含水率25%到15%的主要脱水阶段,叶丝下行床干燥过程内孔容积的收缩明显低于滚筒干燥。2烤烟和白肋烟叶丝体积收缩率与含水率近似为线性关系,干燥至10%含水率时叶丝体积收缩率达25%左右;不同干燥方式对叶丝体积收缩率的变化影响不大。3烤烟和白肋烟叶丝的孔隙体积主要分布在30μm以上的大孔区域;与滚筒干燥相比,下行床干燥方式下两种叶丝在1-10μm直径范围内的孔隙有所增加。

In order to investigate the variation of pore structure in cut strips dried by different drying means, the variation in pore volume, pore size distribution, pore shape and volume of flue-cured and burley tobaccos were dried by a laboratory cylinder dryer and a downflow bed dryer. The results showed that： 1） The pore volume in tobacco dried by different drying means shrank obviously, and the shrinkage of pore volume in flue-cured tobacco was higher than that of burley tobacco. At the stage the moisture content reduced from 25% to 15%, the shrinkage of pore volume in tobacco dried in a downflow bed was remarkably lower than that in a cylinder during drying. 2） The shrinkage of tobacco volume roughly proportioned to the decrease of moisture content in tobacco, the shrinkage reached up to 25% at the moisture content of 10%.Drying means did not affect the shrinkage of tobacco volume significantly. 3） The majority of pores in tobacco were macropores above 30 μm in diameter. Comparing with cylinder drying,more pores of 1-10 μm in diameter emerged in tobacco dried in a downflow bed.