基于毛细渗透原理的铁矿粉接触角测量分析

Analysis of Iron Ore Contact Angle Measurement Based on Capillary Penetration Techniques

铁矿粉与水的接触角对其制粒行为具有重要影响,采用渗透压差法测量接触角已被广泛应用。渗透压差法测定铁矿粉与水的接触角过程中要用一种液体作为基准进行测试得到料柱结构参数,再利用该参数对铁矿粉与水的接触角进行测量和计算,测试过程中料柱结构参数的重现性对测试结果至关重要。本文通过理论分析发现渗透压差法测量粉体接触角过程中影响料柱结构参数β的因素主要有:原料粒度组成、料柱高度和料柱孔隙率。通过实验测试了不同粒度、料柱高度和孔隙率条件下料柱的结构参数β值,发现颗粒粒度对于β值影响较大,适宜测量的颗粒粒度范围为120~200目。用环己烷作为完美润湿液体,对20种铁矿粉与水的接触角进行测试,发现在保证每个测试料柱原料粒度组成、料柱高度和料柱孔隙率分别相同的情况下计算得到的料柱结构参数基本一致,其变化范围为0.5~0.7。选取真密度值介于中间的铁矿粉的料柱结构参数作为所有原料的料柱结构参数,用一步法计算得到铁矿粉与水接触角。对于每种铁矿粉,常规法与一步法计算结果基本吻合。

The ore contact angle play a significant role in granulation operations.Capillary penetration techniques were widely used to determine the wettability of sphalerite particles.The method requires the preparation of two beds of powder.One of these beds is used to follow the capillary rise with a perfectly wetting liquid giving access to a bed structure parameter.The other bed is used with the liquid of interest and the capillary rise data is analyzed using the previously determined structure parameter to obtain the contact angle.The reproducibility of the powder packed bed is of great importance in measurement.Through the theoretical analysis,it confirms that the influence factors of bed structure parameters include size distribution,height and porosity of the bed.Structure parameters for different bed height,particle size and bed porosity were obtained using cyclohexane as a perfectly wetting liquid.Particle size distribution exerted great influence on bed structure parameter.The satiable particle size distribution ranges from 120 to 200 mesh.Contact angles of 20 iron ore powders were measured by penetration method using cyclohexane as perfectly wetting liquid.It was found that bed structure parameters of 20 iron ore powders are nearly equal(range from 0.5 to 0.7)under the condition that the above-mentioned three factors of each bed are respectively the same.We choose the bed structure parameters of iron ores whose density is in the middle as common value of all ores,and then use this common structure parameters to calculate contact angle directly.For each iron ore,the calculated contact angles by one step method are consistent with the traditional calculation.