Cohesiveness and Flowability Properties of Silica Gel Powder

Problem statement: The measurement of powder flowability is a major concern for most industrial processes that deal with the handling of bulk solids as raw materials, intermediates, or products. Approach: The influence of particle size on the flowability of silica gel was investigated using aerated and non-aerated methods. The aerated method involved the measurement of the Hausner Ratio (HR) and Angle Of Repose (AOR) using a Hosokawa Powder Tester (PT-S), while the non-aerated method involved a Cohesion Index (CI) measurement based on a Stable Micro Systems TA.XT Plus texture analyzer. The mean size diameters of the fine and coarse powders used in this work were 9.4 and 60 µm, with densities of 2.1262 and 2.1290 gm cm^-3, respectively. The experiments were conducted immediately after drying with a range of sizes of the chosen powder. Results: The three measured parameters confirmed the general expectation that the fine powders are cohesive and the coarse powders are free-flowing. The HR values indicated that the mixture was a free-flowing one above the 40 µm size. A transition in flowability occurred when the size was between 28 and 40 µm, while the mixture became cohesive when the particle size was below 28 µm. All three of the flowability indicators corresponded well with each other, signifying that the selected indicators correctly predicted the flowability. Conclusion: The new non-aerated method, where CI was measured, was proven to be a reliable indicator in predicting flow characteristics.