Simple De-Aeration Tests

Besides the de-aeration tests in fluidization, there is a very simple test employed in industry to assess aeratability of a bulk solid, and also the rate of de-aeration. 

A simple procedure is to place a sample of the powder in a glass container, usually a measuring cylinder of 2 litre capacity, with the top closed tightly. The container and the sample is then vigorously shaken, usually by repeated inversion, for one minute 

The rate of de-aeration can sometimes also be measured in this way, by noting the volume change of the solids with time this is only possible with solids of extended de-aeration times and the measurement is rather crude even then. It is a quick estimate method, however, and its accuracy may be improved by making a video recording of the settling of the solids. It seems, however, that if such more sophisticated recording of the measurement is to be made, it would warrant the use of a more reproducible experimental set-up than just manual shaking, i.e. the de-aeration test based on fluidization. 

The above described procedure is only used as a first estimate of powder aerability and, as it is merely a relative measurement, it probably does not need to be standardized other than within a particular organization or industry. For more reproducible and accurate results, the de-aeration test by fluidization described in the previous section is recommended. 

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Although flooding is clearly associated with aeration and deaeration, de-aeration or fluidization tests alone are not sufficient to establish floodability. A long de-aeration time and large bed expansion observed in a simple de-aeration test usually, but not always76, coincide with a high likelihood of flooding. 

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