Measurements for characterisation of powder flowability

Characterising the flowability of powder is an important aspect when working with bulk materials. Several measurements are used for this purpose, including the Hosokawa powder test. This test includes seven mechanical measurements and three auxiliary measurements to assess the flowability of the powder. By evaluating the properties of the powder, the transition from a static to a dynamic state can be determined. The results of these measurements are assigned to standardised indices based on extensive analysis of thousands of bulk materials. This article discusses the various measurements and highlights the importance of flowability and floodability of powder. Read on to learn more about these measurements and how they help characterise powder.

What measurements are used to characterise the flowability of powder?

Different measurements are used to characterise the flowability of powders. In the case of unrestricted powder flow analysis, powders can be measured by flow through an orifice or by using the Hosokawa powder test. In the Hosokawa powder test, the flowability of the powder is characterised by seven mechanical measurements and three auxiliary measurements. This provides a numerical evaluation of a powder’s properties by determining its flowability and floodability when transitioning from a static to a dynamic state. The measured values are assigned indices based on standardised analysis of about 3,000 different bulk materials by R.L. Carr.

The measurements used to characterise powder flowability include:

• Angle of shear (Angle of repose): characterises flowability in relation to the cohesion of the material.
• Compressibility (Compressibility): indicates the difference between the aerated and compacted density of the material; low compression indicates good flowability.
• Angle of spatula (Angle of spatula): related to the relative angle of internal friction of the bulk powder.
• Angle of fall (Angle of fall): changes the angle of inclination of the cone or heap material by applying vibration.
• Dispersibility (Dispersibility): represents the sum of the volatility, dustiness and coil characteristics of the powder.
• Angle of difference (Angle of difference): the difference between the angle of shear and the angle of fall; a large value indicates that the material has the characteristics of coils.
• Supporting measurements include aerated bulk density, compacted bulk density and uniformity.

These measurements provide insight into the flowability and floodability of powder. The flowability of powder can be determined through these measurements and evaluation of powder properties.

Catalyst characterisation

At Delft Solids Solutions, we offer several catalyst characterisation services, including chemisorption. Chemisorption is a powerful method to obtain quantitative information about the active metal phase of a (supported) metal catalyst, such as metal surface area, metal distribution and average metal crystallite size. During a chemisorption experiment, the sample is first reduced in hydrogen and then evacuated to obtain the active metal phase. Then, known amounts of hydrogen or carbon monoxide are dosed and absorbed at different partial pressures, resulting in a chemisorption isotherm. By repeating the isotherm measurement after an evacuation step, the difference between the two isotherms can be used to calculate the active metal surface area. Together with metal charge information, the metal distribution and average metal crystallite size can also be calculated. Our chemisorption measurements are performed on a Quantachrome Autosorb-1C adsorption analyser or Autosorb iQ system. The results of a catalyst characterisation measurement by chemisorption usually consist of a graphical representation of the chemisorption isotherms and tabular data providing information on the active metal surface area, metal distribution and average crystallite size. Contact us for more information on our chemisorption services and catalyst characterisation.